RESUMO
BACKGROUND: The systemic renin-angiotensin system (RAS) promotes the plasmatic production of angiotensin (Ang) II, which acts through interaction with specific receptors. There is growing evidence that local systems in various tissues and organs are capable of generating angiotensins independently of circulating RAS. The aims of this study were to investigate the expression and localization of RAS components in rat gingival tissue and evaluate the in vitro production of Ang II and other peptides catalyzed by rat gingival tissue homogenates incubated with different Ang II precursors. METHODS: Reverse transcription-polymerase chain reaction assessed mRNA expression. Immunohistochemical analysis aimed to detect and localize renin. A standardized fluorimetric method with tripeptide hippuryl-histidyl-leucine was used to measure tissue angiotensin-converting enzyme (ACE) activity, whereas high performance liquid chromatography showed products formed after the incubation of tissue homogenates with Ang I or tetradecapeptide renin substrate (TDP). RESULTS: mRNA for renin, angiotensinogen, ACE, and Ang II receptors (AT(1a), AT(1b), and AT(2)) was detected in gingival tissue; cultured gingival fibroblasts expressed renin, angiotensinogen, and AT(1a) receptor. Renin was present in the vascular endothelium and was intensely expressed in the epithelial basal layer of periodontally affected gingival tissue. ACE activity was detected (4.95 +/- 0.89 nmol histidyl-leucine/g/minute). When Ang I was used as substrate, Ang 1-9 (0.576 +/- 0.128 nmol/mg/minute), Ang II (0.066 +/- 0.008 nmol/mg/minute), and Ang 1-7 (0.111 +/- 0.017 nmol/mg/minute) were formed, whereas these same peptides (0.139 +/- 0.031, 0.206 +/- 0.046, and 0.039 +/- 0.007 nmol/mg/minute, respectively) and Ang I (0.973 +/- 0.139 nmol/mg/minute) were formed when TDP was the substrate. CONCLUSION: Local RAS exists in rat gingival tissue and is capable of generating Ang II and other vasoactive peptides in vitro.
Assuntos
Gengiva/metabolismo , Sistema Renina-Angiotensina/fisiologia , Angiotensinogênio/análise , Angiotensinas/análise , Animais , Células Cultivadas , Cromatografia Líquida de Alta Pressão , Endotélio Vascular/metabolismo , Epitélio/metabolismo , Fibroblastos/metabolismo , Fluorometria , Gengiva/citologia , Imuno-Histoquímica , Masculino , Oligopeptídeos/metabolismo , Peptidil Dipeptidase A/análise , Periodontite/metabolismo , Periodontite/patologia , RNA Mensageiro/análise , Ratos , Ratos Wistar , Receptor Tipo 1 de Angiotensina/análise , Receptor Tipo 2 de Angiotensina/análise , Renina/análise , Reação em Cadeia da Polimerase Via Transcriptase ReversaAssuntos
Artrite Infecciosa , Infecções por Pasteurella , Pasteurella multocida , Animais , Humanos , Masculino , Antibacterianos/uso terapêutico , Artrite Infecciosa/microbiologia , Artrite Infecciosa/tratamento farmacológico , Infecções por Pasteurella/tratamento farmacológico , Infecções por Pasteurella/microbiologia , Pessoa de Meia-IdadeRESUMO
Several pieces of evidence indicate that elastase-2 (ELA2; chymotrypsin-like ELA2) is an alternative pathway to the generation of angiotensin II (ANGII). Elastase-2 knockout mice (ELA2KO) exhibit alterations in the arterial blood pressure and heart rate. However, there is no data on the behavioral consequences of ELA2 deletion. In this study, we addressed this question, submitting ELA2KO and wild-type (WT) mice to several models sensitive to anxiety- and depression-like, memory, and repetitive behaviors. Our data indicates a higher incidence of barbering behavior in ELA2KO compared to WT, as well as an anxiogenic phenotype, evaluated in the elevated plus maze (EPM). While a decrease in locomotor activity was observed in ELA2KO in EPM, this feature was not the main source of variation in the other parameters analyzed. The marble-burying test (MBT) indicated increase in repetitive behavior, observed by a higher number of buried marbles. The actimeter test indicated a decrease in total activity and confirmed the increase in repetitive behavior. The spatial memory was tested by repeated exposure to the actimeter in a 24-h interval. Both ELA2KO and WT exhibited decreased activity compared to the first exposure, without any distinction between the genotypes. However, when submitted to the cued fear conditioning, ELA2KO displayed lower levels of freezing behavior in the extinction session when compared to WT, but no difference was observed during the conditioning phase. Increased levels of BDNF were found in the prefrontal cortex but not in the hippocampus of ELA2KO mice compared to WT. Finally, in silico analysis indicates that ELA2 is putatively able to cleave BDNF, and incubation of the purified enzyme with BDNF led to the degradation of the latter. Our data suggested an anxiogenic- and antidepressant-like phenotype of ELA2KO, possibly associated with increased levels of BDNF in the prefrontal cortex.
Assuntos
Antidepressivos/metabolismo , Ansiedade/enzimologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Córtex Pré-Frontal/metabolismo , Serina Endopeptidases/deficiência , Animais , Comportamento Animal , Simulação por Computador , Condicionamento Psicológico , Medo , Feminino , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fenótipo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Recombinantes/farmacologia , Serina Endopeptidases/genética , Serina Endopeptidases/metabolismoRESUMO
A soluble angiotensin (Ang) II-generating enzyme has been purified to homogeneity from the rat mesenteric arterial bed (MAB) perfusate by a combination of gel filtration and affinity chromatographies. The enzyme is a glycoprotein of 28.5 kDa (SDS-PAGE), whose N-terminal sequence is identical with that of the rat pancreatic elastase-2; therefore the enzyme will henceforth be referred to as rat MAB elastase-2. When Ang I was used as the substrate, the enzyme specifically released Ang II and the dipeptide His-Leu (Km=36 microM; Kcat=1530 min-1). The catalytic efficiency (Kcat/Km=42.5 min-1 microM-1) of this reaction was comparable to those of other known Ang I-converting enzymes. The proteolytic specificity of the purified enzyme toward mellitin, oxidized insulin B chain, somatostatin-14 and renin substrate tetradecapeptide suggested that the enzyme-substrate interaction was defined by an extended substrate binding site, typical of elastases-2 of pancreatic origin. According to the sensitivity of the rat MAB elastase-2 to various inhibitors this enzyme could be described as a member of the chymostatin-sensitive group of Ang II-forming serine proteases. The localization and biochemical properties of this enzyme suggest that it might play a role in the regional control of vascular tonus.
Assuntos
Artéria Mesentérica Superior/enzimologia , Elastase Pancreática/química , Elastase Pancreática/isolamento & purificação , Peptidil Dipeptidase A/química , Peptidil Dipeptidase A/isolamento & purificação , Sequência de Aminoácidos , Angiotensina I/metabolismo , Angiotensina II/biossíntese , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Animais , Cromatografia de Afinidade , Cromatografia em Gel , Cinética , Masculino , Dados de Sequência Molecular , Elastase Pancreática/antagonistas & inibidores , Peptidil Dipeptidase A/metabolismo , Perfusão , Ratos , Ratos Wistar , Inibidores de Serina Proteinase/farmacologia , Especificidade por SubstratoRESUMO
The aim of the present study was to evaluate the effect of amiodarone on mean arterial pressure (MAP), heart rate (HR), baroreflex, Bezold-Jarisch, and peripheral chemoreflex in normotensive and chronic one-kidney, one-clip (1K1C) hypertensive rats (N = 9 to 11 rats in each group). Amiodarone (50 mg/kg, iv) elicited hypotension and bradycardia in normotensive (-10 +/- 1 mmHg, -57 +/- 6 bpm) and hypertensive rats (-37 +/- 7 mmHg, -39 +/- 19 bpm). The baroreflex index (deltaHR/deltaMAP) was significantly attenuated by amiodarone in both normotensive (-0.61 +/- 0.12 vs -1.47 +/- 0.14 bpm/mmHg for reflex bradycardia and -1.15 +/- 0.19 vs -2.63 +/- 0.26 bpm/mmHg for reflex tachycardia) and hypertensive rats (-0.26 +/- 0.05 vs -0.72 +/- 0.16 bpm/mmHg for reflex bradycardia and -0.92 +/- 0.19 vs -1.51 +/- 0.19 bpm/mmHg for reflex tachycardia). The slope of linear regression from delta pulse interval/deltaMAP was attenuated for both reflex bradycardia and tachycardia in normotensive rats (-0.47 +/- 0.13 vs -0.94 +/- 0.19 ms/mmHg and -0.80 +/- 0.13 vs -1.11 +/- 0.13 ms/mmHg), but only for reflex bradycardia in hypertensive rats (-0.15 +/- 0.02 vs -0.23 +/- 0.3 ms/mmHg). In addition, the MAP and HR responses to the Bezold-Jarisch reflex were 20-30% smaller in amiodarone-treated normotensive or hypertensive rats. The bradycardic response to peripheral chemoreflex activation with intravenous potassium cyanide was also attenuated by amiodarone in both normotensive (-30 +/- 6 vs -49 +/- 8 bpm) and hypertensive rats (-34 +/- 13 vs -42 +/- 10 bpm). On the basis of the well-known electrophysiological effects of amiodarone, the sinus node might be the responsible for the attenuation of the cardiovascular reflexes found in the present study.
Assuntos
Amiodarona/farmacologia , Antiarrítmicos/farmacologia , Células Quimiorreceptoras/efeitos dos fármacos , Hemodinâmica/efeitos dos fármacos , Hipertensão Renal/fisiopatologia , Animais , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Doença Crônica , Eletrofisiologia , Frequência Cardíaca/efeitos dos fármacos , Masculino , Ratos , Ratos WistarRESUMO
We examined the angiotensin-induced potentiation of noradrenergic transmission in the isolated mesenteric arteries of one-kidney, one clip (1K1C) hypertensive rats. The angiotensin converting enzyme activity measured in plasma did not change during the development of hypertension, whereas the activity measured in the aortic tissue was significantly augmented 28 days after the renal artery was clipped. Although the pressor responses to nerve stimulation were basically unaltered, a significant increase in the sensitivity to norepinephrine developed during hypertension. The 1K1C preparations presented an increased sensitivity to the facilitatory effect of angiotensin II on the response to periarterial nerve stimulation. The facilitatory effect of angiotensin II on both nerve stimulation and exogenous norepinephrine was blocked by saralasin. Angiotensin I induced similar facilitatory action on noradrenergic transmission that was inhibited by saralasin. When a high concentration of angiotensin I was used, the facilitatory effect was significantly higher in mesenteric arteries from 1K1C rats than in controls. Captopril reduced the facilitatory effect of angiotensin I in 1K1C preparations, whereas the responses of the normotensive control rats were unaffected by captopril. These findings are consistent with angiotensin I acting directly on angiotensin II receptors or with angiotensin I being converted to angiotensin II by an alternative pathway not involving angiotensin converting enzyme.
Assuntos
Angiotensina II/farmacologia , Hipertensão Renovascular/fisiopatologia , Norepinefrina/fisiologia , Transmissão Sináptica/efeitos dos fármacos , Animais , Aorta/enzimologia , Pressão Sanguínea/fisiologia , Captopril/farmacologia , Sinergismo Farmacológico , Masculino , Peptidil Dipeptidase A/sangue , Ratos , Ratos Endogâmicos , Saralasina/farmacologia , Simpatomiméticos/farmacologia , Vasoconstrição/efeitos dos fármacosRESUMO
To assess the role of the vascular angiotensin II-generating system in one-kidney, one clip hypertension, we determined the angiotensin converting enzyme activity in plasma and vascular tissues and examined the pressor response to angiotensin II, angiotensin I, and tetradecapeptide renin substrate in isolated mesenteric arteries from one-kidney, one clip hypertensive rats 7 and 30 days after clipping the renal artery and in mesenteric arteries from age-matched normotensive rats. Angiotensin converting enzyme activity, determined in aortic and mesenteric tissues, was significantly augmented in the hypertensive (30 days after clipping) group, whereas plasma activity was normal. The vasoconstrictor responses elicited by angiotensin I and tetradecapeptide in arteries from hypertensive rats were found to be significantly potentiated 30 days after clipping, whereas the angiotensin II responses were basically unchanged. Saralasin completely blocked the vasoconstrictor responses, whereas captopril blocked only the responses to angiotensin I without affecting the responses elicited by angiotensin II and tetradecapeptide. Enalapril, an angiotensin converting enzyme inhibitor given intravenously to unanesthetized rats, significantly lowered the blood pressure of hypertensive rats. The pressor responses elicited by angiotensin II, angiotensin I, and tetradecapeptide were completely inhibited by saralasin, whereas enalapril blocked only the responses of angiotensin I but not those elicited by angiotensin II and tetradecapeptide. These results indicate that local formation of angiotensin II is increased in arteries of one-kidney, one clip hypertensive rats. The data obtained with tetradecapeptide renin substrate suggest an important role for nonrenin proteases in vascular angiotensin II formation.
Assuntos
Angiotensina II/metabolismo , Vasos Sanguíneos/metabolismo , Hipertensão Renovascular/metabolismo , Angiotensina I/farmacologia , Angiotensina II/farmacologia , Angiotensinogênio/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Captopril/farmacologia , Enalapril/farmacologia , Hipertensão Renovascular/fisiopatologia , Técnicas In Vitro , Masculino , Artérias Mesentéricas/metabolismo , Peptidil Dipeptidase A/sangue , Peptidil Dipeptidase A/metabolismo , Ratos , Ratos Endogâmicos , Valores de Referência , Saralasina/farmacologiaRESUMO
We have shown that angiotensin I (AI) conversion as well as bradykinin (BK) inactivation and reactivity are altered in chronic renal hypertensive rats. In the present experiments we tested the possibility that acute renal hypertension or AI and AII infusion cause alterations in both systems. Pulmonary inactivation of BK was estimated by comparing intravenous and intraaortic equipressor doses (20 mm Hg), and the extent of AI conversion was assessed by determining the equipressor doses of AI and AII that produced a 20 mm Hg rise in mean arterial pressure (MAP). Acute renal hypertension was produced by unclamping the renal pedicle (URP) occluded for 5 hours in conscious rats. Before URP, the MAP was already increased (131 +/- 2 mm Hg) and captopril (10 mg/kg, i.v.) produced a fall of 27 +/- 8 mm Hg, suggesting that the renin-angiotensin system was overactive. After URP, MAP rose to 151 +/- 3 mm Hg, and captopril completely abolished the hypertension. Before URP, reactivity to BK was increased [doses 6 times smaller than control (C), 34 +/- 5 ng], and URP produced no further elevation. Pulmonary BK inactivation (97.5% +/- 4%) was the same before and after URP. Before URP, doses of AII 5 times greater than C (2 +/- 4 pmol) were necessary, and hyporeactivity to AII was markedly increased after URP (doses 300 times larger than C). After URP, the conversion was maximal (104% +/- 2% vs 49% +/- 3% in C), and it was already elevated before URP (82% +/- 10%) when six of the nine rats studied had maximal extent of conversion.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Angiotensina I/metabolismo , Angiotensinas/metabolismo , Bradicinina/metabolismo , Hipertensão Renal/fisiopatologia , Sistema Renina-Angiotensina , Doença Aguda , Angiotensina I/administração & dosagem , Angiotensina II/administração & dosagem , Animais , Feminino , Hipertensão Renal/metabolismo , Pulmão/metabolismo , Masculino , Peptidil Dipeptidase A/metabolismo , Ratos , Ratos EndogâmicosRESUMO
Bradykinin is a potent vasodilator peptide; however, its half-life in vivo is very short because of various plasma and tissue peptidases that hydrolyze bradykinin to inactive fragments. We studied the role of kininase II (angiotensin converting enzyme) and neutral endopeptidase 24.11 (enkephalinase) in the catabolism of bradykinin in vascular tissue by determining the effect of inhibitors of kininase II (captopril) and of endopeptidase 24.11 (phosphoramidon) on the action of bradykinin on rat isolated mesenteric arteries. Because bradykinin may induce prostaglandin formation and release, we also studied the effect of a cyclooxygenase inhibitor, indomethacin, on the action of bradykinin. The mesenteric bed was isolated from rats (250-300 g) with rats under either anesthesia and was perfused with Krebs' solution (4 ml/min) containing phenylephrine (0.5-1.0 microgram/ml) to produce a mean perfusion pressure of 120-130 mm Hg. Bradykinin (2.5-40.0 ng), injected as a bolus, produced a dose-dependent decrease in perfusion pressure. In the presence of indomethacin (1.0 microgram/ml), the amplitude of the vasodilator responses to bradykinin was not significantly affected, although the duration of the responses was increased approximately two to four times. In the presence of captopril (1.0 microgram/ml), bradykinin elicited either a vasodilator or a biphasic effect. The vasodilator effect was greatly potentiated by captopril, whereas the duration of the response was unchanged when compared with control experiments. When present, the pressor responses were also dose related. In the presence of indomethacin plus captopril, bradykinin produced only a fall in perfusion pressure that lasted five to six times longer than without any treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Bradicinina/farmacologia , Artérias Mesentéricas/efeitos dos fármacos , Animais , Captopril/farmacologia , Sinergismo Farmacológico , Indometacina/farmacologia , Masculino , Prostaglandinas/biossíntese , Ratos , Ratos Endogâmicos , Fatores de Tempo , Vasodilatação/efeitos dos fármacosRESUMO
Rat pregnancy is associated with a blunted response to vasocontrictors both in vivo and in vitro as well as a decrease in arterial pressure. We examined the influence of pregnancy on neurally induced vasoconstrictor and vasodilator responses of the isolated mesenteric arterial bed from normotensive Wistar and spontaneously hypertensive nonpregnant and 20-day pregnant rats and determined the possible role of nitric oxide (NO) in modulating these responses. MAP (mm Hg) in pregnant normotensive (98+/-1, n=13) and hypertensive (136+/-5, n=13) rats was lower (P<.05) than in nonpregnant controls (114+/-2, n=14, and 174+/-3, n=12, respectively). In isolated mesenteric arterial beds, electrical field stimulation (EFS; 34 V, 3 ms, 10-64 Hz) of perivascular nerves at basal tone induced a frequency-dependent increase in perfusion pressure that was significantly (P<.001) greater in preparations from hypertensive compared with normotensive rats. Pregnancy was associated with a significant decrease in the maximal vasoconstrictor response elicited by EFS in both normotensive and hypertensive groups compared with their nonpregnant controls. In phenylephrine-preconstricted mesenteric beds, EFS (60 V, 1 ms, 1-8 Hz) elicited a similar frequency-dependent decrease in perfusion pressure in normotensive and hypertensive groups, but pregnancy did not influence these responses. In the presence of the NO synthase inhibitor N(omega)-nitro-L-arginine (200 micromol/L), the maximal vasoconstrictor response induced by EFS was significantly (P<.001) augmented in both normotensive and hypertensive groups, and the differences observed between pregnant and nonpregnant groups were abolished. Responses to sodium nitroprusside were not affected by pregnancy, although they were greater in preparations from hypertensive rats. These results indicate that NO contributes to pregnancy-associated diminished vasoconstrictor response to sympathetic stimulation in the mesenteric arterial bed of both normotensive and hypertensive rats.
Assuntos
Hipertensão/fisiopatologia , Artérias Mesentéricas/fisiologia , Óxido Nítrico/fisiologia , Prenhez/fisiologia , Sistema Nervoso Simpático/fisiologia , Vasoconstrição , Animais , Feminino , Nitroarginina/farmacologia , Gravidez , Ratos , Ratos Endogâmicos SHR , Ratos WistarRESUMO
Increased blood pressure responsiveness to bradykinin in comparison with other vasodilator agents was demonstrated in rats with long-term one-kidney and two-kidney, one clip hypertension. In the present study, we analyzed the reactivity to intra-aortically injected bradykinin in unanesthetized one-kidney, one clip hypertensive rats during the control period and 1, 5, and 8 hours after reversal of hypertension after removal of the renal artery constriction. One and 5 hours after unclipping the renal artery, the mean blood pressure decreased markedly (from 195 +/- 7 to 124 +/- 8 and 145 +/- 9 mm Hg, respectively), whereas the hyperreactivity to bradykinin reverted only slightly, and the responses to nitroprusside remained unchanged. In another group of hypertensive rats examined 8 hours after unclipping (pressure decreased from 192 +/- 4 to 143 +/- 8 mm Hg), the hyperreactivity to bradykinin had partially reverted. Significantly larger doses of bradykinin were necessary to produce the same decrease in blood pressure when compared with the control period (16.4 +/- 2.0 vs. 7.2 +/- 1.2 ng). The same degree of reversal of hyperreactivity to bradykinin was observed when the blood pressure of hypertensive rats was reduced (from 207 +/- 8 to 143 +/- 5 mm Hg) during 1 hour by hydralazine injection. Complete reversibility of bradykinin hyperreactivity was produced by nitroprusside infusion (from 201 +/- 13 to 142 +/- 10 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Pressão Sanguínea/efeitos dos fármacos , Bradicinina/farmacologia , Hipertensão Renal/fisiopatologia , Animais , Constrição , Relação Dose-Resposta a Droga , Hidralazina/farmacologia , Masculino , Nitroprussiato/farmacologia , Ratos , Ratos Endogâmicos , Artéria Renal/fisiopatologia , Vasodilatadores/farmacologiaRESUMO
Administration (3 to 100 microg/kg IV) of clonidine, rilmenidine, and an imidazoline derivative, 2-(2-chlorophenylamino)imidazoline, in pithed nonstimulated rabbits caused a dose-dependent increase in mean arterial pressure without affecting heart rate. Prazosin (0.1 mg/kg IV) almost abolished the pressor responses to 2-(2-chlorophenylamino)imidazoline, partially inhibited those induced by clonidine, but failed to affect those elicited by rilmenidine. In contrast, yohimbine (1 mg/kg IV) blunted the pressor responses of the 3 drugs. In sympathetically stimulated pithed rabbits, 2-(2-chlorophenylamino)imidazoline induced only pressor effects, whereas clonidine and rilmenidine caused a transient pressure increase followed by a dose-dependent depressor effect. Yohimbine abolished the depressor effect of both drugs, which may have involved presynaptic alpha(2)-adrenoceptors. In conclusion, peripheral effects of 2-(2-chlorophenylamino)imidazoline and clonidine involved at least alpha(1)- and alpha(2)-adrenoceptor activation, whereas pressor and depressor effects of rilmenidine were mediated by alpha(2)-adrenoceptors.
Assuntos
Anti-Hipertensivos/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Fenômenos Fisiológicos Cardiovasculares , Clonidina/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Imidazóis/farmacologia , Oxazóis/farmacologia , Sistema Nervoso Simpático/fisiologia , Animais , Pressão Sanguínea/fisiologia , Estimulação Elétrica , Frequência Cardíaca/fisiologia , Masculino , Coelhos , Rilmenidina , Transmissão SinápticaRESUMO
We investigated the role of nitric oxide on rapid (25- and 40-minute) baroreceptor resetting during the onset of acute hypertension in rats treated with NG-nitro-L-arginine, an inhibitor of nitric oxide synthesis, and methylene blue, an inhibitor of guanylate cyclase. The effect of treatment with glibenclamide, an ATP-dependent K+ channel blocker, was also investigated. Arterial hypertension was provoked in a ramp progression by the drug NG-nitro-L-arginine alone or in association with aortic coarctation. Whole aortic nerve activity and carotid pressure were recorded in the anesthetized rats. The extent of rapid resetting was evaluated by means of the ratio (delta Systolic Threshold Pressure/delta Control Diastolic Pressure) x 100 as well as by the extent of displacement of the pressure-nerve activity curve defined by the ratio (delta Mean Arterial Pressure at 50% of maximum activity/delta Mean Arterial Pressure) x 100. All groups gave the same increase in mean arterial pressure at 25 and 40 minutes after the onset of hypertension. A greater extent of resetting to hypertensive levels was observed in the treated groups compared with coarctation alone. At 40 minutes after the onset of hypertension, the coarctation and nitro-L-arginine groups exhibited a further increase in the extent of resetting. The rats submitted to glibenclamide plus coarctation presented a slight but significant decrease in gain. These findings suggest that an active L-arginine-nitric oxide-cyclic GMP pathway blunts rapid resetting during the onset of hypertension. In addition, they also indicate that ATP-dependent K+ channels can also modulate rapid resetting of the baroreceptors to hypertensive levels.
Assuntos
Aorta/inervação , Arginina/análogos & derivados , Arginina/fisiologia , Pressão Sanguínea/fisiologia , GMP Cíclico/fisiologia , Azul de Metileno/farmacologia , Músculo Liso Vascular/inervação , Óxido Nítrico/fisiologia , Pressorreceptores/fisiologia , Análise de Variância , Animais , Coartação Aórtica , Arginina/farmacologia , Pressão Sanguínea/efeitos dos fármacos , GMP Cíclico/antagonistas & inibidores , Glibureto/farmacologia , Guanilato Ciclase/antagonistas & inibidores , Masculino , Óxido Nítrico/antagonistas & inibidores , Nitroarginina , Pressorreceptores/efeitos dos fármacos , Ratos , Ratos WistarRESUMO
In conscious chronic (12 to 18 weeks) streptozotocin diabetic rats, we examined the changes in basal heart rate, with particular attention to heart rate variability assessed by evaluating the standard deviation (bpm) of the lengths of adjacent pulse pressure. We also investigated in anesthetized rats the ability of the aortic baroreceptors to acutely (30 minutes) reset to hypertensive levels. For this purpose, pressure-nerve activity curves for the baroreceptors were obtained, and gain (slope of the curve) and mean arterial pressure at 50% of maximal baroreceptor activity were calculated. The shift of the pressure-nerve activity curve was used as an index of resetting. Conscious diabetic rats (n=6) exhibited lower mean arterial pressure (93+/-6 versus 109+/-4 mm Hg), heart rate (272+/-25 versus 359+/-11 bpm), and heart rate variability (18+/-7 versus 36+/-6 bpm) than control rats (n=7). Under anesthesia, diabetic rats (n=7) and control rats (n=8) exhibited similar mean arterial pressure (113+/-6 versus 109+/-7 mm Hg in control rats ), mean arterial pressure at 50% of maximal baroreceptor activity (117+/-5 versus 107+/-6 bpm), gain (1.66+/-0.08 versus 1.81+/-0.05%/mm Hg), and extent of resetting (44+/-12 versus 49+/-9%) to hypertensive levels. The present study demonstrated that conscious chronic diabetic rats presented lower heart rate variability than control rats. On the other hand, chronic diabetes was not associated with alterations in baroreceptor function or its ability to rapidly reset to hypertensive levels.
Assuntos
Diabetes Mellitus Experimental/fisiopatologia , Frequência Cardíaca , Pressorreceptores/fisiopatologia , Animais , Doença Crônica , Masculino , Ratos , Ratos Wistar , Reflexo , EstreptozocinaRESUMO
We investigated the acute and chronic effects of converting enzyme inhibitors (captopril or enalapril) and of angiotensin II receptor blockade (DuP 753) on rapid (30-minute) baroreceptor resetting elicited by a prompt and sustained hypertensive response provoked by aortic constriction. Pressure-nerve activity curves, pressure at 50% of maximal baroreceptor activity, baroreceptor gain (slope of the curve), and systolic threshold pressure for baroreceptor activation were determined as indexes of baroreceptor function. A slight fall in mean arterial pressure after acute treatment with the converting enzyme inhibitor or DuP 753 was accompanied by a partial leftward curve shift, which is associated with a partial threshold shift and increase in gain. A maintained hypertensive stimulus caused a partial rightward curve shift and partial (49% to 56%) threshold shift to hypertensive levels in both acutely treated and control rats. The hypertensive stimulus provoked a partial rightward curve shift and complete (88% to 94%) threshold shift to hypertensive levels in chronically treated rats. The effect of enalapril on baroreceptor function was unaltered by the bradykinin antagonist Hoe 140. These data demonstrate that chronic inhibition of converting enzyme or blockade of angiotensin II receptors facilitates rapid resetting of the baroreceptors to hypertensive levels caused by partial aortic constriction without a change in baroreceptor sensitivity.
Assuntos
Angiotensina II/antagonistas & inibidores , Compostos de Bifenilo/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Captopril/farmacologia , Enalapril/farmacologia , Hipertensão/fisiopatologia , Imidazóis/farmacologia , Pressorreceptores/efeitos dos fármacos , Tetrazóis/farmacologia , Angiotensina I/farmacologia , Angiotensina II/farmacologia , Animais , Aorta/inervação , Bradicinina/farmacologia , Losartan , Masculino , Pressorreceptores/fisiologia , Pressorreceptores/fisiopatologia , Ratos , Ratos Wistar , Valores de Referência , Análise de RegressãoRESUMO
We investigated the role of vasopressin, angiotensin II, and catecholamines in the onset of acute (45-minute) aortic coarctation hypertension in conscious rats. Partial aortic constriction was performed by means of a pneumatic cuff placed around the abdominal aorta above the renal arteries for 15 or 45 minutes. A sham-operated group was used as control. Mean carotid pressure before aortic constriction did not differ between rat groups. Aortic constriction produced a similar increase of mean carotid pressure during 15 minutes (36 +/- 3 to 37 +/- 3 mm Hg above basal levels) and 45 minutes (37 +/- 2 to 39 +/- 3 mm Hg). Plasma vasopressin concentration after 15 minutes of coarctation (4.4 +/- 0.5 pg/mL) did not differ from that observed in control rats (3.0 +/- 0.8 pg/mL), whereas after 45 minutes, it was significantly higher (14.3 +/- 3.3 pg/mL). Plasma renin activity increased significantly after coarctation (21.7 +/- 4.1 and 29.9 +/- 2.9 ng angiotensin I/mL per hour, at 15 and 45 minutes, respectively) when compared with control rats (3.9 +/- 0.5 ng angiotensin I/mL per hour). After coarctation, plasma norepinephrine concentration was consistently reduced, whereas plasma epinephrine concentration did not differ from control rats. In conclusion, these data provide evidence for an effective vasopressor role for vasopressin in the genesis of acute (45-minute) aortic coarctation hypertension in conscious rats. In addition, although the results confirm that the renin-angiotensin system participates earlier in the onset of coarctation hypertension, they rule out a significant vasopressor role for catecholamines in the early development of hypertension.
Assuntos
Coartação Aórtica/fisiopatologia , Pressão Sanguínea , Hipertensão/fisiopatologia , Análise de Variância , Animais , Coartação Aórtica/sangue , Arginina Vasopressina/sangue , Artérias Carótidas/fisiopatologia , Epinefrina/sangue , Hematócrito , Hipertensão/sangue , Hipertensão/etiologia , Masculino , Norepinefrina/sangue , Ratos , Ratos Wistar , Renina/sangue , Fatores de TempoRESUMO
Increase in glucose-6-phosphatase catalytic subunit (G6Pase, G6pc) transcription enhances hepatic glucose production in non-insulin-dependent diabetes mellitus (NIDDM). The fact that carnivorous fish is an alternative model to study NIDDM led us to clone and characterise the first G6pc promoter region reported for fish and non-mammalian animals. The 5'-flanking region of G6pc from gilthead sea bream (Sparus aurata) was isolated by chromosome walking. With SMART RACE-PCR, the transcription start site was located 106 base pairs (bp) upstream of the translational start. Transfection analysis in HepG2 cells located a functional promoter in the 850 bp 5'-flanking isolated fragment (positions -770 to +80 relative to the transcription start). Sequential 5'-deletion analysis of the promoter fragment revealed that a core functional promoter for basal transcription is comprised within the 190 bp upstream of the transcription start site. In vivo, glucose and insulin reduced G6Pase mRNA levels in the fish liver. Transfection experiments in HepG2 cells showed that insulin repressed S. aurata G6pc under high-glucose conditions. Synergistic activation of piscine G6pc promoter was induced by cotransfection with expression plasmids for hepatocyte nuclear factor-4alpha (HNF-4alpha) and peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC-1alpha). No direct relationship was found between PGC-1alpha coactivation of HNF-4alpha transactivation and the repressive effect of insulin. Interestingly, insulin hardly affected G6pc promoter activity in the absence of glucose, suggesting that a reduced capacity of insulin-dependent repression of piscine G6pc may lead to insulin resistance in carnivorous fish.
Assuntos
Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Glucose-6-Fosfatase/genética , Glucose/farmacologia , Insulina/farmacologia , Regiões Promotoras Genéticas/genética , Dourada/genética , Transcrição Gênica/efeitos dos fármacos , Região 5'-Flanqueadora/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Domínio Catalítico , Células Cultivadas , Clonagem Molecular , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/farmacologia , Glucose-6-Fosfatase/metabolismo , Fator 4 Nuclear de Hepatócito , Humanos , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Fosfoproteínas/farmacologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Fatores de Transcrição/farmacologia , Transcrição Gênica/genéticaRESUMO
We have demonstrated that the isolated perfused rat mesenteric arterial bed (MAB) secretes peptidases capable of metabolizing bradykinin and angiotensin I. The major degradative pathway of bradykinin by enzymes found in the rat MAB perfusate was mediated by carboxypeptidase A-like activity, whereas angiotensin 1 degradation followed two main routes, one attributable to a carboxypeptidase A-like enzyme and the other to an endopeptidase. This latter enzyme seems to be a novel serine peptidase capable of releasing angiotensin II directly from both angiotensin I and renin substrate tetradecapeptide. The rat MAB perfusate was also shown to contain additional endo- and exopeptidases that might play a role in the metabolism of other vasoactive peptides. Our finding that isolated rat MAB secretes peptidases into the perfusion medium indicates that peptide processing within the microvasculature environment may be effected by enzymes besides those normally found in plasma or associated with cell membranes.
Assuntos
Peptídeo Hidrolases/isolamento & purificação , Circulação Esplâncnica , Peptídeo Intestinal Vasoativo/metabolismo , Sequência de Aminoácidos , Angiotensina I/metabolismo , Animais , Bradicinina/metabolismo , Carboxipeptidases/metabolismo , Carboxipeptidases A , Cromatografia em Gel , Endopeptidases/isolamento & purificação , Endopeptidases/metabolismo , Dados de Sequência Molecular , Peptídeo Hidrolases/metabolismo , Perfusão , Ratos , Ratos EndogâmicosRESUMO
1. We used the kinin antagonist HOE 140 to investigate the role of endogenous kinins in the acute antihypertensive effect of the angiotensin converting enzyme inhibitor enalapril in chronic and acute renal hypertensive rats. 2. In normotensive rats, treatment with HOE 140 (33 micrograms/kg, sc) caused a complete blockade of the depressor effect of bradykinin (100 ng, ia) without affecting the depressor effect of sodium nitroprusside (1 microgram, i.v.) or the basal blood pressure. 3. HOE 140 treatment (33 micrograms/kg, sc, plus 330 ng/min, i.v.) did not affect basal blood pressure of chronic (6-7 weeks) one-kidney, one clip and two-kidney, one clip hypertensive rats and in rats with acute hypertension, elicited by unclamping the renal pedicle that had been occluded for 5 h, but HOE 140 completely blocked the hypotensive response to bradykinin (100 ng, ia) during the 60-min period after enalapril administration (2 mg/kg, i.v.). 4. Acutely hypertensive rats treated or not with HOE 140 (33 micrograms/kg, sc, plus 330 ng/min, i.v.) presented a similar fall in blood pressure after enalapril (165 +/- 5 to 137 +/- 6 mmHg and 166 +/- 5 to 136 +/- 6 mmHg, respectively). 5. Untreated two-kidney, one clip hypertensive rats presented a rapid and sustained fall in blood pressure after enalapril (177 +/- 4 to 148 +/- 4 mmHg) that did not differ from the HOE 140-treated (33 micrograms/kg, sc, plus 330 ng/min, i.v.) group (177 +/- 6 to 154 +/- 4 mmHg). 6. One-kidney, one clip hypertensive rats treated with HOE 140 (33 micrograms/kg, sc, plus 330 ng/min, i.v.) showed a significantly smaller fall in blood pressure after enalapril (204 +/- 7 to 179 +/- 9 mmHg) compared to the untreated rats (197 +/- 7 to 149 +/- 2 mmHg). 7. These results indicate that kinin potentiation plays an important role in the antihypertensive effect of acutely administered angiotensin converting enzyme inhibitor in the one-kidney, one clip model of hypertension.
Assuntos
Enalapril/uso terapêutico , Hipertensão Renal/tratamento farmacológico , Cininas/fisiologia , Análise de Variância , Inibidores da Enzima Conversora de Angiotensina/administração & dosagem , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Bradicinina/administração & dosagem , Bradicinina/análogos & derivados , Bradicinina/antagonistas & inibidores , Bradicinina/farmacologia , Bradicinina/fisiologia , Enalapril/administração & dosagem , Enalapril/farmacologia , Cininas/antagonistas & inibidores , Masculino , Ratos , Ratos Wistar , Fatores de TempoRESUMO
1. The relationship of plasma angiotensin converting enzyme (ACE) activity to changes in the extent of angiotensin I (ANG I) conversion in vivo in rats with short-term and chronic (8 weeks) hypertension was examined. 2. Plasma ACE activity was measured by a fluorimetric assay and the extent of ANG I conversion was calculated from the equipressor doses of ANG I and ANG II in conscious rats. 3. The extent of ANG I conversion was higher in chronic one-kidney, one clip hypertensive rats than in the normotensive age-matched control rats (64.1 +/- 3.6% vs 34.8 +/- 5.2%), while no difference was found in the ACE activity measured in plasma from both groups. 4. In rats with acute hypertension, produced upon unclamping the renal pedicle occluded for 5 hours, the extent of ANG I conversion was increased when compared to the period prior to renal pedicle occlusion (from 38.8 +/- 4.1% to 68.6 +/- 8.5%), and plasma ACE activity remained unchanged. 5. These results indicate that circulating ACE cannot be used as an index of ANG I conversion in vivo and support the proposal that tissue ACE is responsible for the augmented ANG I conversion observed in vivo in both acute renal hypertension and chronic one-kidney, one clip hypertension.