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1.
Circulation ; 82(4): 1494-504, 1990 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-2401078

RESUMO

The in vivo quantification of myocardial muscarinic receptors has been obtained in six closed-chest dogs by using positron emission tomography. The dogs were injected with a trace amount of 11C-labeled methylquinuclidinyl benzilate (MQNB), a nonmetabolized antagonist of the muscarinic receptor. This was followed 30 minutes later by an injection of an excess of unlabeled MQNB (displacement experiment). Two additional injections of unlabeled MQNB with [11C]MQNB (coinjection experiment) and without [11C]MQNB (second displacement experiment) were administered after 70 and 120 minutes, respectively. This protocol allowed a separate evaluation of the quantity of available receptors (B'max) as well as the association and dissociation rate constants (k+1 and k-1) in each dog. The parameters were calculated by using a nonlinear mathematical model in regions of interest over the left ventricle and the interventricular septum. The average value of B'max was 42 +/- 11 pmol/ml tissue, the rate constants k+1, k-1, and Kd were 0.6 +/- 0.1 ml.pmol-1.min-1, 0.27 +/- 0.03 ml.pmol-1.min-1, and 0.49 +/- 0.14 pmol.ml-1, respectively, taking into account the MQNB reaction volume estimated to 0.15 ml/ml tissue. Although [11C]MQNB binding would appear irreversible, our findings indicate that the association of the antagonist is very rapid and that the dissociation is far from negligible. The dissociated ligand, however, has a high probability of rebinding to a free receptor site instead of escaping into the microcirculation. We deduce that the positron emission tomographic images obtained after injecting a trace amount of [11C]MQNB are more representative of blood flow than of receptor density or affinity. We also suggest a simplified protocol consisting of a tracer injection of [11C]MQNB and a second injection of an excess of cold MQNB, which is sufficient to measure B'max and Kd in humans.


Assuntos
Miocárdio/análise , Receptores Muscarínicos/análise , Tomografia Computadorizada de Emissão , Animais , Sangue/metabolismo , Radioisótopos de Carbono , Simulação por Computador , Cães , Feminino , Masculino , Modelos Cardiovasculares , Receptores Muscarínicos/metabolismo , Fatores de Tempo
3.
Endocrinology ; 127(4): 1727-34, 1990 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-2169399

RESUMO

We have previously raised an anti-c-erb A peptide antibody (designated 4B II) which immunoprecipitated in vitro transcription/translation products of c-erb A alpha 1 and beta. 4B II could recognize nuclear T3 receptor (NT3R) without distinction between difference in species and tissues. Using 4B II, we studied immunohistochemical localization of NT3R proteins in various tissues of the rat. Cryostat sections (4-6 microns) of selected rat tissues were incubated with 4B II at 4C overnight, followed by fluorescein-isothyocianate-conjugated anti-rabbit immunoglobulin G for 60 min at 25 C. The cellular localization of fluorescence in all tissues examined was exclusively nuclear. Under the same conditions, control sections stained with antiserum which had previously absorbed with c-erb A peptide or inactive serum showed no specific staining. In the brain the large nuclei, supposed to be neuronal, were strongly stained in the cerebral cortex and the granular layer of the cerebellum. In the kidney, cells in the glomerulus, the distal, but not the proximal, tubules, and the collecting ducts exhibited nuclear staining. Nuclear fluorescence was observed homogeneously in the heart and liver, but the intensity was much weaker in the latter. Less intense fluorescence was seen in the testis and spleen, although specific immunostaining was clearly observed in the nuclei of spermatocytes, Leydig cells, and the heads of the sperms in the testis, and many lymphocytes in the spleen. Nuclei of follicular cells of the thyroid exhibited very strong fluorescence, suggesting existence of plenty of NT3R proteins. The anterior pituitary showed strong immunostaining in most nuclei, and clear nuclear fluorescence was also detected in the intermediate lobe of the pituitary. The present study showed that NT3R distributes selectively in certain types of cells in many tissues and that the content of NT3R proteins seems to correlate with the concentration of c-erb A mRNA alpha 1 and beta among many organs.


Assuntos
Núcleo Celular/análise , Proteínas Proto-Oncogênicas/análise , Receptores dos Hormônios Tireóideos/análise , Sequência de Aminoácidos , Animais , Química Encefálica , Imunofluorescência , Soros Imunes , Imuno-Histoquímica , Rim/análise , Fígado/análise , Linfócitos/análise , Masculino , Dados de Sequência Molecular , Miocárdio/análise , Proteínas Proto-Oncogênicas/imunologia , Ratos , Ratos Endogâmicos , Receptores dos Hormônios Tireóideos/imunologia , Espermatozoides/análise , Baço/análise
4.
Biochem J ; 270(2): 545-8, 1990 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-2400400

RESUMO

HL-60 cells possess a 60 kDa Ca2(+)-binding protein that is contained in a discrete subcellular compartment, referred to as calciosomes. Subcellular fractionation studies have suggested that, in HL-60 cells, this intracellular compartment is an Ins(1,4,5)P3-sensitive Ca2+ store. In order to investigate the structural relationship of the 60 kDa Ca2(+)-binding protein of HL-60 cells to other Ca2(+)-binding proteins, we have purified the protein by ammonium sulphate extraction, acid precipitation, and DEAE-cellulose and phenyl-Sepharose column chromatography. The N-terminal sequence of the protein shows 93% identity with rabbit muscle calreticulin, a recently cloned sarcoplasmic reticulum Ca2(+)-binding protein. No amino acid sequence similarity with calsequestrin was found, although the purified protein cross-reacted with anti-calsequestrin antibodies. The calreticulin-related protein of HL-60 cells might play a role as an intravesicular Ca2(+)-binding protein of an Ins(1,4,5)P3-sensitive Ca2+ store.


Assuntos
Proteínas de Ligação ao Cálcio/isolamento & purificação , Cálcio/metabolismo , Inositol 1,4,5-Trifosfato/farmacologia , Organelas/análise , Sequência de Aminoácidos , Animais , Calreticulina , Calsequestrina , Fracionamento Celular , Cromatografia , Humanos , Immunoblotting , Leucemia Promielocítica Aguda , Dados de Sequência Molecular , Peso Molecular , Músculos/análise , Miocárdio/análise , Coelhos , Homologia de Sequência do Ácido Nucleico , Células Tumorais Cultivadas
5.
Am J Vet Res ; 51(9): 1345-8, 1990 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2396781

RESUMO

Mean carnitine concentrations [( carnitine]) were higher (P less than 0.05) in adult cats than in kittens for skeletal muscle (total and free carnitine), myocardium (free carnitine), and urine (total and free carnitine). The free/total carnitine ratio was lower (P less than 0.05) in kittens than in adults for liver, myocardium, and urine. Carnitine concentrations were similar between genders in kittens, but in adult cats, [carnitine] in plasma (total, free, and esterified carnitine) and liver (total and free carnitine) were higher (P less than 0.05) in female than in male cats. Total and free plasma [carnitine] were correlated to total and free liver [carnitine], respectively. Skeletal muscle [carnitine] was not correlated to plasma [carnitine]. Correlations in [carnitine] between plasma and myocardium, kidney, or urine were inconsistent.


Assuntos
Carnitina/análise , Gatos , Animais , Carnitina/sangue , Carnitina/urina , Gatos/sangue , Gatos/urina , Feminino , Rim/análise , Fígado/análise , Masculino , Músculos/análise , Miocárdio/análise
6.
Circ Res ; 67(3): 780-3, 1990 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2397580

RESUMO

To investigate the contributions of humoral and hemodynamic factors to cardiac adaptations associated with chronic exercise, female Fischer 344 rats were subjected to chronic swimming, infrarenal cardiac transplantation, or both. Swimming resulted in hypertrophy (11-12%) of the in situ hearts in both the unoperated and operated animals compared with the matched sedentary controls. The cardiac isograft exhibited atrophy (32-35%), which was not attenuated by swimming. The cardiac isograft was also associated with a decrease in the percent of V1 myosin isoenzyme, which was attenuated by swimming (45 +/- 5% versus 66 +/- 6%). Swimming also increased the percent of this isomyosin in the in situ hearts of operated rats. These data suggest that hemodynamic load and/or neural innervation are necessary for hypertrophy associated with chronic conditioning by swimming, whereas myosin isoenzyme control is significantly mediated by humoral factors.


Assuntos
Adaptação Fisiológica , Transplante de Coração , Coração/fisiologia , Miocárdio/análise , Miosinas/análise , Natação , Animais , Atrofia , Feminino , Rejeição de Enxerto , Hemodinâmica , Hipertrofia , Miocárdio/patologia , Ratos , Ratos Endogâmicos F344 , Transplante Isogênico
7.
Circ Res ; 67(3): 753-63, 1990 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2168817

RESUMO

Studies conducted in our laboratory have demonstrated that activated immune cells produce a soluble inhibitor(s) of cardiac myocyte contractile and cyclic AMP (cAMP) responses to beta-adrenergic stimulation. To examine the mechanism of this effect, metabolic assays were conducted on cultured rat cardiac myocytes incubated in the presence and absence of supernatants harvested from rat activated splenocyte cultures. Intracellular cAMP accumulation in response to isoproterenol was inhibited by up to 74% in a dose-dependent fashion by conditioned media containing soluble cytokines from activated immune cells. By use of myocyte cultures in which contaminating nonmyocyte proliferation was inhibited by nonlethal irradiation, this phenomenon was shown to be independent of mitogenic effects. Isobutylmethylxanthine, a phosphodiesterase inhibitor, did not ablate cytokine-induced inhibition of cAMP accumulation. Parameters of beta-adrenergic receptor binding and affinity were also unaffected. cAMP suppression was maintained after cholera toxin stimulation of cAMP production via stimulatory G protein ADP-ribosylation. cAMP inhibition was not apparent when cells were stimulated with forskolin, a direct adenylate cyclase activator. Importantly, pertussis toxin treatment significantly ablated cytokine-induced cAMP inhibition. Thus, interference with agonist-occupied beta-adrenergic receptor coupling to adenylate cyclase to produce cAMP and subsequent contractile responses is induced by a factor(s) elaborated by activated immune cells. This interference occurs at the level of signal transduction across the membrane, can be overridden by pertussis toxin, and may involve changes in the coupling of the stimulatory/inhibitory G proteins to adenylate cyclase. These results demonstrate a novel mechanism of cytokine-induced myocyte dysfunction and may have important pathophysiological ramifications in immune-mediated myocardial diseases.


Assuntos
Fatores Biológicos/farmacologia , AMP Cíclico/análise , Isoproterenol/farmacologia , Miocárdio/metabolismo , Transdução de Sinais , Toxina Adenilato Ciclase , Adenilil Ciclases/análise , Animais , Células Cultivadas , Meios de Cultura , Citocinas , Isoproterenol/antagonistas & inibidores , Miocárdio/análise , Miocárdio/citologia , Toxina Pertussis , Ensaio Radioligante , Ratos , Receptores Adrenérgicos beta/efeitos dos fármacos , Fatores de Virulência de Bordetella/farmacologia
8.
Circ Res ; 67(3): 764-9, 1990 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2168818

RESUMO

This study aimed to determine whether receptors for endothelin were present on the cardiac myocyte as well as on vascular smooth muscle cells. Low- and high-resolution autoradiography was performed using 125I-endothelin 1 on intact rat myocardium and samples of human ventricle obtained from explanted hearts at the time of transplant. In addition to specific binding to the smooth muscle of the blood vessel lumen, there was considerable binding associated with cardiac myocytes. To discover whether there was any functional correlate for this binding, muscle cells were isolated enzymatically from human and rat ventricle and from rat femoral artery, and their contractile characteristics were studied. Single cardiac cells were superfused with physiological saline at 32 degrees C, and their length change was displayed continuously on a chart recorder. Endothelin 1 had a pronounced effect on shortening in both rat and human myocytes. The contraction amplitude was approximately doubled in both cases, from 4.1 +/- 0.8% cell length to 8.1 +/- 1.3% for rat (mean +/- SEM, n = 9, p less than 0.001), and from 2.1 +/- 0.5% to 4.0 +/- 0.5% in human (n = 10, p less than 0.001). In rat, the magnitude of the effect was comparable to that of the alpha-adrenoceptor agonist phenylephrine. The maximum contraction amplitude of the human cells, produced by raising extracellular calcium to greater than 10 mM, was 11.4 +/- 1.1% cell length (n = 9), significantly greater than that produced by endothelin (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Músculo Liso Vascular/análise , Miocárdio/análise , Receptores de Superfície Celular/análise , Animais , Autorradiografia , Sítios de Ligação , Técnicas Histológicas , Humanos , Técnicas In Vitro , Masculino , Músculo Liso Vascular/citologia , Músculo Liso Vascular/metabolismo , Contração Miocárdica , Miocárdio/citologia , Miocárdio/metabolismo , Fenilefrina/farmacologia , Ratos , Ratos Endogâmicos , Receptores de Superfície Celular/metabolismo , Receptores de Endotelina
9.
Hepatology ; 12(3 Pt 1): 481-5, 1990 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2169452

RESUMO

Cardiac responses to catecholamines are known to be attenuated in chronic liver disease. To elucidate the role of beta-adrenergic receptor alteration in this phenomenon, we measured heart rate responsiveness to isoprenaline and myocardial beta-adrenergic receptor-binding characteristics in three groups of rats: those that were sham operated, those that had portal vein stenosis and those that were cirrhotic because of bile duct ligation. Responsiveness to isoprenaline was evaluated in conscious rats by the dose of isoprenaline needed to increase basal heart rate by 50 beats/min and by the maximal heart rate response. beta-Receptor characteristics in heart membranes were derived from 125I-iodocyanopindolol binding data. Compared with sham-operated controls, cirrhotic rats needed a significantly higher dose of isoprenaline to raise basal heart rate by 50 beats/min (102.3 +/- 19.1 vs. 28.3 +/- 11.3 ng/kg) and lower maximal heart rate response (104 +/- 29 vs. 158 +/- 61 beats/min). In addition, myocardial beta-receptor density was significantly lower in cirrhotic rats (26.5 +/- 4.6 vs. 37.5 +/- 10.3 fmol/mg protein) and the dissociation constant was higher (31.6 +/- 17.0 vs. 14.0 +/- 2.5 pmol/L). Analysis of beta 1/beta 2 subpopulations revealed that the decreased total beta-receptor density was entirely due to selective beta 1-receptor down-regulation. beta-Receptor affinity for agonist was not altered in cirrhotic rats. Rats with portal vein stenosis showed no significant differences in either isoprenaline responsiveness or beta-receptor characteristics when compared with controls. These results indicate that beta-adrenergic receptor down-regulation may be responsible for the myocardial hyporesponsiveness to catecholamines observed in cirrhosis.


Assuntos
Cirrose Hepática Experimental/metabolismo , Miocárdio/metabolismo , Receptores Adrenérgicos beta/metabolismo , Animais , Modelos Animais de Doenças , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/fisiologia , Coração/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Hipertensão Portal/metabolismo , Hipertensão Portal/fisiopatologia , Isoproterenol/farmacologia , Cirrose Hepática Experimental/fisiopatologia , Masculino , Miocárdio/análise , Ensaio Radioligante/métodos , Ratos , Ratos Endogâmicos , Receptores Adrenérgicos beta/análise , Receptores Adrenérgicos beta/efeitos dos fármacos
10.
Circ Res ; 67(3): 564-73, 1990 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2204498

RESUMO

Increasing evidence suggests that the renin-angiotensin system modulates cardiovascular homeostasis both via its circulating, plasma-borne components and through locally present, tissue-resident systems with site-specific activity. The existence of such a system in the heart has been proposed, based on biochemical studies as well as on the demonstration of renin and angiotensinogen messenger RNA in cardiac tissue. We conducted the present study to determine whether biologically active angiotensin peptides may be cleaved within the heart from locally present angiotensinogen. Isolated, perfused rat hearts were exposed to infusions of purified hog renin; the coronary sinus effluent was collected and subsequently assayed for angiotensin I (Ang I) and angiotensin II (Ang II) by high-pressure liquid chromatography and specific radioimmunoassay. Both Ang I and II were undetectable under control conditions but appeared promptly after the addition of renin. Dose-dependent peak values for Ang I release ranged from 2.42 +/- 0.65 fmol/min to 1.38 +/- 0.18 pmol/min during renin infusions at concentrations between 10 microunits/ml and 5 milliunits/ml. Ang II levels measured in the perfusate reflected a mean fractional intracardiac conversion of Ang I to Ang II of 7.18 +/- 1.09%. Generation of Ang I and Ang II was inhibited in the presence of specific inhibitors of renin and converting enzyme, respectively. To investigate the source of angiotensinogen, we measured spontaneous angiotensinogen release from isolated perfused hearts. In the absence of renin in the perfusate, angiotensinogen was initially released in high, but rapidly declining, concentrations and subsequently at a low, but stable, rate. Prior perfusion with angiotensinogen-rich plasma resulted in enhanced early angiotensinogen release but did not alter the second, delayed phase, suggesting that, in addition to plasma-derived substrate, locally produced angiotensinogen may also participate in the intracardiac formation of angiotensin. Supporting this interpretation, hearts from animals pretreated with dexamethasone showed increased angiotensinogen messenger RNA concentrations as well as increased rates of angiotensinogen release not only during the early but also during the late phase. Our study newly demonstrates that Ang I and II may be formed within the isolated heart from locally present substrate, which appears to be derived in part from the circulating pool and in part from endogenous synthesis. These findings add support to the concept of a functionally active and locally integrated cardiac renin-angiotensin system and emphasize its potential physiological and pathological relevance.


Assuntos
Angiotensinogênio/análise , Coração/fisiologia , Miocárdio/análise , Sistema Renina-Angiotensina/fisiologia , Angiotensina I/análise , Angiotensina II/análise , Angiotensinogênio/genética , Animais , Captopril/farmacologia , Dexametasona/farmacologia , Feminino , Técnicas In Vitro , Perfusão , RNA Mensageiro/análise , Ratos , Ratos Endogâmicos WKY , Renina/farmacologia
11.
J Nutr ; 120(9): 1068-74, 1990 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2168945

RESUMO

The effect on copper status of diets containing homocysteine, an intermediate in the transsulfuration pathway of methionine metabolism, was investigated in rats. Two groups of six male weanling Sprague-Dawley rats were provided with deionized water and pair-fed diets that were adequate (14.0 mg/kg) or deficient (1.3 mg/kg) in Cu to groups fed diets similarly adequate or deficient in Cu but containing DL-homocysteine (10 g/kg). Hemoglobin concentration, tissue Cu levels and the activities of the Cu-dependent enzymes--ceruloplasmin, superoxide dismutase and cytochrome c oxidase--were markedly lowered by Cu-deficient diets and by homocysteine. These dietary treatments also lowered the activity of glutathione peroxidase and produced concomitant increases in the activity of manganese-dependent superoxide dismutase and iron levels in the liver. However, dietary homocysteine decreased hepatic Mn and low Cu diets decreased cardiac iron content. Moreover, both dietary treatments significantly lowered kidney Fe levels. Homocysteine increased heart, liver and kidney weights (g/100 g body tissue) and greatly elevated the level of thiobarbituric acid reactive substances (TBARS) in heart tissue. These results indicate that dietary homocysteine can markedly lower Cu status in rats and result in tissue redistribution of Fe and increased cardiac levels of TBARS, a measure of lipid peroxidation.


Assuntos
Cobre/análise , Dieta , Homocisteína/farmacologia , Animais , Ceruloplasmina/análise , Cobre/deficiência , Complexo IV da Cadeia de Transporte de Elétrons/análise , Glutationa Peroxidase/análise , Homocisteína/administração & dosagem , Ferro/análise , Rim/análise , Fígado/análise , Masculino , Manganês/análise , Miocárdio/análise , Tamanho do Órgão , Distribuição Aleatória , Ratos , Ratos Endogâmicos , Superóxido Dismutase/análise , Zinco/análise
12.
J Neurochem ; 55(2): 379-85, 1990 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-2370544

RESUMO

Histamine H1-receptors, visualized in the guinea pig heart by autoradiography using [125I]iodobolpyramine as a specific probe, are abundant in the nodal tissue and cardiac vessels but also occur heterogeneously in the myocardium. Following photoaffinity labeling with [125I]iodoazidophenpyramine and electrophoresis, the ligand binding domain of the heart H1-receptor was shown to be present on a major 68-kDa and a less abundant 54- to 58-kDa protein. The 68-kDa protein displayed a molecular size higher in heart than in all other tissues (56 kDa). This indicates the existence of at least two isoforms of the H1-receptor; the cardiac isoform, however, was pharmacologically indistinguishable from the common isoform studied in cerebellar membranes using available ligands. Its distinct electrophoretic properties suggest that the cardiac isoform may have a unique function.


Assuntos
Miocárdio/metabolismo , Receptores Histamínicos H1/metabolismo , Marcadores de Afinidade , Animais , Autorradiografia , Membrana Celular/análise , Membrana Celular/metabolismo , Cerebelo/metabolismo , Clorfeniramina/farmacologia , Eletroforese em Gel de Poliacrilamida , Cobaias , Átrios do Coração/análise , Átrios do Coração/metabolismo , Íleo/análise , Íleo/metabolismo , Radioisótopos do Iodo , Pulmão/análise , Pulmão/metabolismo , Masculino , Mianserina/farmacologia , Peso Molecular , Miocárdio/análise , Fotoquímica , Pirilamina/análogos & derivados , Pirilamina/metabolismo , Pirilamina/farmacologia , Succinimidas/metabolismo
13.
J Clin Pathol ; 43(8): 650-3, 1990 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-2401733

RESUMO

Myocardial calcium overload was observed in a patient with giant cell myocarditis. The myocardial calcium content estimated by atomic absorption spectrophotometry amounted to 120 mEq/kg dry weight, and the von Kossa stain disclosed multiple foci with patchy calcifications of myocardial fibres. Cytochemical examination of the ultrastructural calcium localisation using the phosphate-pyroantimonate method showed considerable variation in the subcellular calcium distribution. In normal myocytes calcium precipitates were confined to the inner leaflet of the sarcolemma, T-tubules, intercalated disks, and sporadically to mitochondria. In contrast, extensive calcification of mitochondria and loss of sarcolemmal calcium was evident in necrotic myocytes. A number of grossly normal myocytes also showed an increase of calcium precipitates in slightly swollen mitochondria. These findings suggest that myocardial calcium overload in this case started in viable myocytes and was not merely a secondary phenomenon occurring after cell death.


Assuntos
Calcinose/complicações , Miocardite/complicações , Calcinose/patologia , Cálcio/análise , Células Gigantes/ultraestrutura , Humanos , Masculino , Microscopia Eletrônica , Pessoa de Meia-Idade , Dilatação Mitocondrial , Miocardite/patologia , Miocárdio/análise , Miocárdio/ultraestrutura
14.
Magn Reson Med ; 15(1): 25-32, 1990 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2374497

RESUMO

Tm(DOTP)5-, the thulium(III) complex of 1,4,7,10-tetraazacyclododecane-N,N',N',N'''-tetra(methylenephos p hon ate), is introduced as a 23Na+ shift agent for use in discrimination of the NMR resonances of intra- and extracellular 23Na+ ions in perfused rat hearts. The novel shift agent is directly compared to the widely used Dy(TTHA)3- (dysprosium(III) triethylenetetraminehexaacetate).


Assuntos
Espectroscopia de Ressonância Magnética , Miocárdio/análise , Oxazóis , Pirimidinonas , Sódio/análise , Túlio , Animais , Coração , Indicadores e Reagentes , Perfusão , Ratos
15.
Magn Reson Med ; 15(1): 33-44, 1990 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2374498

RESUMO

Intracellular [Na+], [H+], and [ATP] and mechanical performance were measured in the isovolumic perfused rat heart during ischemia. The concentration of intracellular sodium, [Na+]i, was determined by atomic absorption spectroscopy under control conditions, and [Na+]i was monitored by 23Na NMR spectroscopy at 1-min intervals under control conditions and during global ischemia. [ATP], [H+], and [Pi] were measured by 31P NMR in a separate group under identical conditions. The control [Na+]i measured by atomic absorption was 30.7 +/- 3.3 mM (mean +/- SD, n = 6), and [Na+]i measured by NMR was 6.2 +/- 0.5 mM (n = 3). Brief ischemia (10 min) was associated with a 54% increase in [Na+]i which reversed completely with reperfusion. Developed pressure also returned to control values upon reperfusion. Prolonged ischemia (30 min) produced continuous further accumulation of sodium (0.53 mM/min, r2 = 0.99). [H+] also increased approximately linearly early in ischemia (0.084 microM/min, r2 = 0.97). The rate of increase in [Na+]i was more than 4000 times greater than the increase in [H+] on a molar basis. Nevertheless, [H+]/[Na+]i increased early in ischemia because the proportional change in [H+] was greater than that in [Na+]i. These results indicate that (1) intracellular sodium measured by NMR in the functioning heart is about 20% of total intracellular sodium; (2) intracellular acidosis and accumulation of sodium develop simultaneously during global ischemia; (3) increased intracellular sodium content is not in itself an indicator of irreversible injury; and (4) recovery of mechanical performance is associated with return of [Na+]i (measured by NMR) to baseline after brief ischemia. The mechanism of the increase in sodium content detected by NMR is unknown.


Assuntos
Doença das Coronárias/metabolismo , Miocárdio/análise , Sódio/análise , Animais , Coração , Espectroscopia de Ressonância Magnética , Masculino , Oxazóis , Perfusão , Pirimidinonas , Ratos , Ratos Endogâmicos , Espectrofotometria Atômica , Túlio
16.
Magn Reson Med ; 15(1): 70-80, 1990 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2374501

RESUMO

Angina is characterized by brief periods of ischemia followed by reperfusion; the cumulative effect of these episodes on energetics of the myocardium has not been fully elucidated. This study used an in vivo feline model for the assessment of high-energy phosphate compounds during brief sequential periods of ischemia and reperfusion. Nine adult, open-chest, anesthetized cats were prepared with a reversible occluder around the proximal left anterior descending artery and a 1.2-cm-inside diameter coil sutured on the myocardial surface in the distribution of the left anterior descending coronary artery. Levels of PCr, Pi, and ATP (beta-phosphate signal) were measured by 31P MRS in a GE CSI 2-T NMR spectrometer/imager. Measurements were obtained during a control period and during three successive occlusion-deocclusion periods of roughly 12 and 20 min' duration, respectively. The last deocclusion period was observed for 60 min. Electron microscopy was performed in two animals. PCr declined (P less than 0.01) rapidly following each occlusion to 51 +/- 5.2% (occlusion 1), 53 +/- 5.8% (occlusion 2), and 48 +/- 5.7% (occlusion 3) of the control value by 6 min. Pi rose (P less than 0.01) with the three sequential occlusions to 253 +/- 46, 288 +/- 57, and 277 +/- 46%, respectively. PCr and Pi returned to baseline promptly with reperfusion, while ATP showed a gradual decline throughout the experiment, decreasing to 77 +/- 7.2% of control at the end of the last reperfusion (P less than 0.05). Although PCr returned to baseline during reperfusion, ATP did not, suggesting a reduction in the nucleotide pool. These findings indicate that the repeated episodes of ischemia, which are insufficient to produce necrosis, can have an effect on myocardial high-energy phosphate metabolism as evidenced by mild depletion of ATP.


Assuntos
Trifosfato de Adenosina/análise , Doença das Coronárias/diagnóstico , Espectroscopia de Ressonância Magnética , Miocárdio/análise , Fosfatos/análise , Fosfocreatina/análise , Animais , Gatos
17.
Am J Physiol ; 259(1 Pt 2): H109-15, 1990 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2375397

RESUMO

Cholinergic vasoconstriction in vivo and the influence of resting cholinergic activity on basal coronary tone were investigated by measuring coronary blood flow, cardiac function, and blood gases during either acetylcholine injection, muscarinic receptor blockade, or vagal ligation, in open-chest chloralose-urethan-anesthetized swine. Intracoronary injections of acetylcholine (0.5-3.0 micrograms) caused significant (P less than 0.05) dose-dependent reductions in coronary blood flow (19.0-75.5%) and conductance (14.3-78.2%). Atropine (200 micrograms) completely blocked these responses. Cholinergic mediation of basal coronary tone was initially evaluated by determining the effects of muscarinic blockade with intracoronary injection of atropine (200 micrograms). Intracoronary injection of atropine had no significant effects on coronary blood flow or conductance. Finally, to ensure that parasympathetically released acetylcholine was not overcoming the muscarinic blockade, vagal ligation was performed during pacing. Neither coronary blood flow nor conductance was significantly altered by vagal ligation. The present studies demonstrate that acetylcholine induces a muscarinic vasoconstriction of coronary arteries in the domestic swine. However, these studies do not support a role for parasympathetic mediation of basal coronary vascular tone.


Assuntos
Circulação Coronária/fisiologia , Sistema Nervoso Parassimpático/fisiologia , Parassimpatomiméticos/farmacologia , Suínos/fisiologia , Acetilcolina/administração & dosagem , Acetilcolina/farmacologia , Animais , Atropina/farmacologia , Circulação Coronária/efeitos dos fármacos , Feminino , Coração/fisiologia , Hemodinâmica/efeitos dos fármacos , Hemodinâmica/fisiologia , Injeções Intra-Arteriais , Masculino , Miocárdio/análise , Oxigênio/análise , Sistema Nervoso Parassimpático/efeitos dos fármacos , Parassimpatomiméticos/antagonistas & inibidores , Fluxo Sanguíneo Regional/efeitos dos fármacos , Nervo Vago/cirurgia , Vasoconstrição/efeitos dos fármacos
18.
Am J Physiol ; 259(1 Pt 2): R15-20, 1990 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2375425

RESUMO

We measured contractile force of ventricular strips form the turtle Chrysemys picta bellii exposed to 1 h of combined anoxia and acidosis (pH 7.0) at 20 degrees C. Strips either beat spontaneously (self-paced) or in response to electrical stimulation (paced at 12, 24, or 36 beats/min). Tissue [lactate] and intracellular pH (pHi) were measured in control strips and at the end of anoxia-acidosis. In self-paced strips, at normal extracellular Ca2+ concentration ([Ca2+]o) (1 mM), both rate and force fell significantly after 1 h of anoxia-acidosis to 54 and 17.1%, respectively, of control values. Increased [Ca2+]o to 10 mM at 30 min had a small but significant positive effect on both rate and force. Contractile force of paced strips also fell progressively during anoxia-acidosis, but the decrease varied directly with pacing frequency. Under all cases of anoxia-acidosis, pHi fell significantly from the control value of 7.53; in paced strips, acidosis was most severe at 36 beats/min (pHi 6.75), and in self-paced strips, pHi (approximately 6.85) was independent of [Ca2+]o. Based on this and previous work, we conclude that combined anoxia-acidosis, similar to that observed in vivo after prolonged anoxic submergence, profoundly depresses cardiac function. Both hypercalcemia and bradycardia improve performance in this extreme state, but these effects are not as great as when anoxia and acidosis occur alone.


Assuntos
Desequilíbrio Ácido-Base/fisiopatologia , Acidose/fisiopatologia , Coração/fisiologia , Hipóxia/fisiopatologia , Contração Miocárdica/fisiologia , Tartarugas/fisiologia , Animais , Coração/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Ventrículos do Coração/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Hipercalcemia/fisiopatologia , Lactatos/análise , Miocárdio/análise , Função Ventricular
19.
Clin Exp Immunol ; 81(1): 132-6, 1990 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2379317

RESUMO

Previous immunohistochemical work has indicated that terminal C5b-9 complement complexes are selectively deposited in infarcted areas of human myocardium. In the present study, we sought to quantify C5b-9 levels in myocardial tissue, and to differentiate between the membrane-bound C5b-9 (m) and the cytolytically inactive SC5b-9 complex. Paired tissue specimens from infarcted and non-infarcted myocardium were obtained from 36 autopsies. The homogenized and washed tissues were extracted with n-octyl-beta-D-glucopyranoside (octylglucoside) detergent, and the concentrations of C5b-9 in the extracts were determined by ELISA. Membrane-derived C5b-9 (m) and SC5b-9 were differentiated from each other on the basis of their characteristic sedimentation behaviour in sucrose density gradients. It was found that infarcted myocardial tissue contained on average an approximately three-fold higher concentration of C5b-9, compared with non-infarcted tissue. This increase was due in part to an increase in levels of C5b-9 (m). The results corroborate previous immunohistochemical data and show that complement activation occurs to completion with the generation of potentially cytotoxic C5b-9 complexes in infarcted myocardial tissues.


Assuntos
Complexo de Ataque à Membrana do Sistema Complemento/análise , Proteínas do Sistema Complemento/análise , Glicoproteínas/análise , Infarto do Miocárdio/fisiopatologia , Adulto , Idoso , Autopsia , Ensaio de Imunoadsorção Enzimática , Humanos , Pessoa de Meia-Idade , Miocárdio/análise
20.
FEBS Lett ; 268(1): 222-6, 1990 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-2384158

RESUMO

The apparent molecular size of the native alpha-crystallin B in cytosol preparations from rat heart, brain and retina was determined by gel permeation chromatography, detecting the protein by immunochemical assay (ELISA), using an alpha-crystallin specific antiserum. Native alpha-crystallin from cytosol preparations of rat lens cortex was used as a reference. alpha-Crystallin B present in all three cytosol preparations from non-lenticular tissues eluted in a single symmetrical peak, with the same elution volume as alpha-crystallin from lens cortex cytosol preparations, corresponding to an apparent average molecular size of 0.8 x 10(6) Da. No other species could be detected. The results indicate that the alpha-crystallin aggregates characterized by an apparent average molecular mass of 0.8 x 10(6) Da, and considered to be the native, physiological form of the protein in the lens, are indeed not specific to lens tissue. Furthermore, the size of these alpha-crystallin aggregates is independent of their polypeptide composition. Aggregates found in the lens, composed of alpha A and alpha B polypeptides and their respective phosphorylated forms alpha Ap and alpha Bp, are similar in size to those found in heart, brain and retina, containing the alpha B but not the alpha A polypeptide.


Assuntos
Cristalinas/análise , Animais , Química Encefálica , Cromatografia em Gel , Peso Molecular , Miocárdio/análise , Ligação Proteica , Ratos , Ratos Endogâmicos , Retina/análise
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