Pharmacokinetic/pharmacodynamic assessments of 10 mg/kg tramadol intramuscular injection in yellow-bellied slider turtles (Trachemys scripta scripta).

In reptiles, administration of opioid drugs has yielded unexpected results with respect to analgesia. The aims of this study were to assess the pharmacokinetic/pharmacodynamic (PK/PD) properties of tramadol and its active metabolite M1 and to evaluate the effect of the renal portal system on the PK/PD parameters in yellow-bellied slider turtles. Turtles (n = 19) were randomly assigned to four treatment groups, according to a masked, single-dose, four-treatment, unpaired, four-period crossover design. Group A (n = 5) received a single i.m. dose of tramadol (50 mg/mL) at 10 mg/kg in the proximal hindlimb. Group B (n = 5) received the same i.m. dose but in the forelimb. Groups C (n = 5) and D (n = 4) received a single i.m. injection of saline (NaCl 0.9%) of equivalent volume to the volumes of tramadol injected in the hind- and forelimb, respectively. Groups were rotated (1-month washout period) until the completion of the crossover study. Tramadol plasma concentrations were evaluated by a validated HPLC-FL method. An infrared thermal stimulus was applied to the plantar surface of the turtles' hindlimbs to evaluate the thermal withdrawal latency (TWL). The two PK profiles of tramadol differed in the first 2 h following administration, but overlapped in the elimination phases. The metabolite M1 was formed in both the treatment groups, showing similar pharmacokinetic trends, although the amount of M1 was significantly higher (20%) in the hindlimb vs. forelimb group. Turtles given tramadol in the hind- and forelimb showed a significant increase in TWL over the periods of 0.5-48 and 8-48 h, respectively. The calculated % maximal possible response (% MPR) was low (about 24%). The PK/PD correlations between M1 plasma concentrations vs. % MPR appeared to show a counterclockwise hysteresis loop shape.

Bisphenol A and Bisphenol S Oxidative Effects in Sheep Red Blood Cells: An In Vitro Study.

Bisphenols (BPs) are plastic components widely used worldwide and occurring in the environment. Exposure to these compounds is known to be harmful for animals and humans at different levels. The aim of this study was to evaluate and compare the oxidative effects of bisphenol A (BPA) and bisphenol S (BPS) in sheep. Reactive oxygen species (ROS) production and correlated structural alterations in sheep erythrocytes were investigated in vitro. Blood samples from four ewes were collected at fasting from the jugular vein using vacuum collection tubes containing EDTA. For ROS assay in erythrocytes, blood was properly diluted and BPA or BPS was added to obtain final bisphenol concentrations in the range between 1 and 300 µM. 2',7'-Dichlorodihydrofluorescein diacetate (H2DCF-DA) 3 µM was added to the samples, and fluorescence was read in four replicates using a microplate reader. To evaluate erythrocyte shape, blood smears of blood treated with the different concentrations of BPS and BPA were prepared. A significant increase in ROS production was observed when concentrations of BPS and BPA increased from 1 to 100 µM (p < 0.05). At the higher concentrations of the two studied BPs (300 µM of BPS and 200-300 µM of BPA), a ROS decrease was observed when compared to the control group (p < 0.01). Erythrocytes' shape alterations were observed in cells treated with BPS and BPA 200-300 µM 4 hours after the beginning of the treatment. This study confirms that BPA and BPS exhibit oxidative effects on sheep erythrocytes. At higher concentrations, BPA was able to modify erythrocytes' shape, while BPS altered their membrane as a sign of a protein clustering that could lead to eryptosis. These BPs' effects are consequent to intracellular ROS increase.

A kallikrein-like enzyme in the aorta of normotensive and hypertensive rats.

We evaluated whether vascular kallikrein is altered in rats with genetic or experimental hypertension. Group 1 was infused intraperitoneally with angiotensin II (Ang II) or vehicle for 4 weeks; group 2 was injected subcutaneously with deoxycorticosterone (75 mumol/kg once a week) or vehicle for 4 weeks; group 3 consisted of uninephrectomized rats on high sodium intake given deoxycorticosterone or vehicle; and group 4 consisted of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Active and total kallikrein activity was measured in abdominal aortic homogenates using an amidolytic assay. Ang II increased systolic blood pressure at a dose of 400 nmol/kg per day (146 +/- 6 versus 123 +/- 3 mm Hg in controls, P < .01) but not at 80 nmol/kg per day. Deoxycorticosterone did not increase blood pressure except in uninephrectomized rats on high salt (173 +/- 6 versus 135 +/- 4 mm Hg in controls, P < .01). Blood pressure averaged 194 +/- 2 mm Hg in SHR and 123 +/- 3 mm Hg in WKY rats. Vascular kallikrein was similar in rats given Ang II or vehicle. In deoxycorticosterone-treated rats total kallikrein was higher than in controls (9.2 +/- 0.8 versus 3.5 +/- 0.1 pkat/mg protein, P < .05), whereas active kallikrein did not differ (0.09 +/- 0.04 versus 0.09 +/- 0.03 pkat/mg protein, P = NS). A similar pattern was observed in uninephrectomized deoxycorticosterone-treated rats (active, 0.09 +/- 0.03 versus 0.10 +/- 0.04, P = NS; total, 7.4 +/- 0.7 versus 4.1 +/- 0.2 pkat/mg protein, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular effects of brain kinin receptor blockade in spontaneously hypertensive rats.

We studied the role of brain kinins in the regulation of cardiovascular function. Intracerebroventricular injection of 380 pmol bradykinin increased mean blood pressure by 20 +/- 2 mm Hg (P < .01) in normotensive Wistar-Kyoto (WKY) rats. Complete inhibition of this effect was achieved with intracerebroventricular administration of the newly synthesized, long-acting B2 receptor antagonist D-Arg,[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin (Hoe 140). On a molar basis, Hoe 140 was two orders of magnitude more potent than antagonists of the first generation. Baroreceptor sensitivity, estimated as the heart rate response to blood pressure changes induced by intravenous injection of phenylephrine or sodium nitroprusside, was not altered by Hoe 140 in WKY rats. In spontaneously hypertensive rats (SHR), baroreceptor reflex sensitivity to increments in mean blood pressure was reduced by Hoe 140 (mean slope value: -0.47 +/- 0.07 versus -0.92 +/- 0.13 beats per minute per millimeter of mercury in controls, P < .05). Hoe 140 did not affect the tachycardic component of the baroreceptor reflex. Two-week intracerebroventricular infusion of Hoe 140 did not alter systolic blood pressure or heart rate in WKY rats. In SHR, systolic blood pressure increased (P < .01) similarly during the infusion of Hoe 140 or vehicle (from 174 +/- 6 to 220 +/- 5 mm Hg and 178 +/- 4 to 210 +/- 4 mm Hg at 2 weeks, respectively), whereas heart rate did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic inhibition of bradykinin B2-receptors enhances the slow vasopressor response to angiotensin II.

The contribution of endogenous kinins in the regulation of blood pressure of angiotensin-treated rats was evaluated using the new bradykinin B2-receptor antagonist Hoe 140 (D-Arg,[Hyp3,Thi5,D-Tic7, Oic8]-bradykinin). Chronic infusion of Hoe 140 at 75 nmol/d (a dose able to inhibit the vasodepressor effect of an intra-aortic bolus injection of 0.85 nmol/kg bradykinin) did not alter systolic blood pressure (tail-cuff plethysmography). Chronic infusion of angiotensin II (Ang II) induced a dose-related increase in systolic blood pressure and plasma Ang II levels. The vasopressor effect of 40 or 100 nmol/d Ang II was enhanced in rats given chronic infusion of Hoe 140 (by 12 and 14 mm Hg, respectively), whereas the increase in plasma Ang II levels remained unaltered. Furthermore, a low nonpressor dose of Ang II (20 nmol/d) was then able to increase blood pressure during chronic blockade of bradykinin receptors by Hoe 140 (from 126 +/- 3 to 137 +/- 3 mm Hg, P < .05). Combined infusion of 20 nmol Ang II and Hoe 140 did not alter the urinary excretion of sodium and water despite the fact that blood pressure was increased. Potentiation of the pressure effect of Ang II by Hoe 140 was confirmed by direct measurement of mean blood pressure (125 +/- 2 versus 108 +/- 2 mm Hg at 20 nmol, 123 +/- 2 versus 110 +/- 2 mm Hg at 40 nmol, and 139 +/- 2 versus 125 +/- 3 mm Hg at 100 nmol Ang II, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Bradykinin B2-receptor blockade facilitates deoxycorticosterone-salt hypertension.

The contribution of endogenous kinins to the regulation of blood pressure, urinary volume, and renal sodium excretion was evaluated in Wistar rats on high sodium intake by using the new bradykinin receptor antagonist Hoe 140 (D-Arg,[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin). Neither Hoe 140 (3 nmol/hr s.c. for 4 weeks) nor its vehicle altered systolic blood pressure (tail-cuff plethysmography) or renal function in rats given saline solution (0.15 mol/L NaCl) to drink ad libitum. Four-week administration of deoxycorticosterone (DOC), combined with high sodium intake and uninephrectomy, increased systolic blood pressure from 127 +/- 3 to 160 +/- 3 mm Hg (p < 0.01). When long-term infusion of Hoe 140 was combined with DOC, high sodium intake, and uninephrectomy, systolic blood pressure rose from 127 +/- 3 to 175 +/- 3 mm Hg (p < 0.01). The hypertensive effect was greater in the Hoe 140 group (48 +/- 4 versus 33 +/- 3 mm Hg in controls, p < 0.05). This difference was confirmed by direct measurement of mean blood pressure (Hoe 140 group, 154 +/- 4 mm Hg; vehicle group, 139 +/- 4 mm Hg; p < 0.05). The antagonist blunted the increase in urinary volume induced by salt load and DOC in uninephrectomized rats, whereas it did not alter the increase in urinary sodium excretion. These results suggest that endogenous kinins do not play a major role in the regulation of normal blood pressure in sodium-loaded rats, whereas they may attenuate the hypertensive effect induced by long-term administration of mineralocorticoids and salt in uninephrectomized rats.

Early blockade of bradykinin B2-receptors alters the adult cardiovascular phenotype in rats.

We evaluated whether long-term inhibition of bradykinin B2-receptors by the long-acting antagonist Hoe 140 (D-Arg,[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin) affects the blood pressure of normotensive rats. Neither Hoe 140 (at 75 nmol/d for 8 weeks) nor its vehicle altered systolic pressure of adult rats on a normal or high sodium intake. In further experiments, pairs of Hoe 140-treated rats were mated and their offspring maintained on Hoe 140 and a normal sodium diet. Controls were given vehicle instead of Hoe 140. At 9 weeks of age, rats given Hoe 140 during prenatal and postnatal phases of life showed greater systolic pressures, heart rates, and body weights than controls (122 +/- 1 versus 113 +/- 1 mm Hg, 444 +/- 6 versus 395 +/- 8 beats per minute, 258 +/- 7 versus 213 +/- 3 g, respectively, P < .01), whereas urinary creatinine excretion was reduced (1.13 +/- 0.05 versus 1.36 +/- 0.04 mumol/100 g body wt in controls, P < .05). The difference in blood pressure (confirmed by direct intra-arterial measurement) persisted after 20 days of dietary sodium loading, whereas it was nullified by sodium restriction. In additional experiments, the offspring of untreated rats received Hoe 140 or vehicle from 2 days to 11 weeks of age. At this stage, systolic pressure and body weight were significantly greater in Hoe 140-treated rats compared with controls, and heart rate was similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of kinin blockade on the blood pressure of salt-loaded pregnant rats.

We evaluated whether chronic inhibition of bradykinin B2 receptors by the long-acting antagonist D-Arg, [Hyp3, Thi5,D-Tic7,Oic8]-bradykinin (Hoe 140) affects blood pressure of salt-loaded pregnant rats. Pairs of rats fed a high sodium diet (0.84 mmol sodium per gram chow) were mated at 14 weeks of age. Infusion of vehicle or Hoe 140 (300 nmol/d per kilogram body weight) was performed throughout each dam's pregnancy by use of an Alzet osmotic pump implanted in the abdominal cavity. In both groups, no significant change in systolic pressure (tail-cuff plethysmography) or renal blood flow (Doppler flow-meter) was observed from that in the unmated state to that at midterm pregnancy. In the control group, systolic pressure decreased at the 21st day of pregnancy (from 126 +/- 2 to 97 +/- 2 mm Hg, P < .01), and renal blood flow increased (from 6.1 +/- 0.1 to 7.5 +/- 0.2 kHz, P < .01). These changes were nullified by the administration of Hoe 140 (systolic pressure changing from 124 +/- 2 to 118 +/- 4 mm Hg, P = NS; renal blood flow changing from 6.3 +/- 0.2 to 6.2 +/- 0.1 kHz, P = NS). In the group given Hoe 140, placental weight was greater (0.50 +/- 0.01 versus 0.43 +/- 0.01 g in controls, P < .01) and the fetal/placental weight ratio was reduced (4.53 +/- 0.09 versus 5.31 +/- 0.17 in controls, P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Kallikrein-kinin system and blood pressure sensitivity to salt.

We evaluated the blood pressure response to chronic salt loading in a rat strain inbred for low urinary kallikrein excretion. Low-kallikrein rats showed greater systolic blood pressure values (130 +/- 1 versus 114 +/- 2 mm Hg in controls; P < .05) at 9 weeks of age. Systolic blood pressure was increased after 10 days of dietary sodium loading in the low-kallikrein group and remained unchanged in controls (153 +/- 1 versus 112 +/- 2 mm Hg, P < .01). In additional experiments, blood pressure sensitivity to salt was tested in low-kallikrein rats receiving a chronic infusion of rat glandular kallikrein (1.7 micrograms/day per 100 g body weight, IV) or vehicle. Systolic blood pressure of vehicle-treated rats was increased by salt loading (from 138 +/- 1 to 158 +/- 2, 153 +/- 1, and 145 +/- 2 mm Hg at 5, 10, and 15 days, respectively; P < .01), while it remained unchanged in the kallikrein-treated group (from 136 +/- 2 to 146 +/- 5, 140 +/- 2, and 134 +/- 4 mm Hg at 5, 10, and 15 days, respectively; P = NS). Urinary kallikrein excretion was increased by kallikrein infusion (from 13.6 +/- 1.4 to 17.8 +/- 2.1 nanokatals per 24 hours; P < .01). Plasma immunoreactive kallikrein levels were higher in the kallikrein-treated group (66.4 +/- 4.4 versus 57.7 +/- 1.4 ng/mL in vehicle-treated rats; P < .05). On normal sodium diet, the ratio of kidney weight to body weight was lower in low-kallikrein rats (329 +/- 5 versus 370 +/- 8 mg/100 g body weight in controls; P < .01). This difference was associated with a decreased number of glomeruli per unit square area and increased width of Bowman's space. These results indicate that kallikrein replacement prevents the exaggerated blood pressure increase observed in rats with a genetically determined defect in urinary kallikrein excretion. Histological abnormalities are present at different levels in the nephron, and they may be functionally related to the altered cardiovascular and renal phenotype of this strain.

Brain kinins are responsible for the pressor effect of intracerebroventricular captopril in spontaneously hypertensive rats.

The role of the brain kallikrein-kinin system in the regulation of arterial blood pressure of normotensive and spontaneously hypertensive rats was evaluated. Intracerebroventricular administration of the kinin antagonist [DArg0]Hyp3-Thi5,8[DPhe7]bradykinin caused no change in mean blood pressure in Wistar-Kyoto, Sprague-Dawley, or spontaneously hypertensive rats. The antagonist proved to be very potent in blocking the pressor effect of intracerebroventricular bradykinin (32 +/- 3 vs. 3 +/- 1 mm Hg, p less than 0.01). It was specific, as the pressor effect induced by other unrelated peptides was similar during the infusion of either vehicle or kinin antagonist (angiotensin II, 25 +/- 4 vs. 26 +/- 2 mm Hg; prostaglandin E2, 48 +/- 3 vs. 47 +/- 8 mm Hg; norepinephrine, 17 +/- 2 vs. 18 +/- 2 mm Hg; leucine-enkephaline, 15 +/- 2 vs. 16 +/- 1 mm Hg; neurotensin, 18 +/- 2 vs. 19 +/- 1 mm Hg; substance P, 19 +/- 2 vs. 19 +/- 2 mm Hg). Intracerebroventricular administration of 1 mg captopril, an inhibitor of kininase II (one of the enzymes responsible for kinin degradation), caused no change in mean blood pressure in normotensive rats, whereas it increased mean blood pressure by 44 +/- 9 mm Hg (p less than 0.01) in spontaneously hypertensive rats. This increase in mean blood pressure was blocked and then reversed into a hypotensive effect (22 +/- 6 mm Hg, p less than 0.05) during the infusion of kinin antagonist. Our data suggest that the pressor effect induced by intracerebroventricular captopril is due to a transient elevation in endogenous brain kinin levels, supporting the hypothesis that the brain kallikrein-kinin system plays a role in the central regulation of blood pressure in spontaneously hypertensive rats.

Role of nitric oxide synthase inhibition in the acute hypertensive response to intracerebroventricular cadmium.

1. In the rat, intracerebroventricular (i.c.v.) injection of cadmium, a pollutant with long biological half-life, causes a sustained increase in blood pressure at doses that are ineffective by peripheral route. Since cadmium inhibits calcium-calmodulin constitutive nitric oxide (NO) synthase in cytosolic preparations of rat brain, this mechanism may be responsible for the acute pressor action of this heavy metal. 2. To test this possibility, we evaluated the effect of i.c.v. injection of 88 nmol cadmium in normotensive unanaesthetized Wistar rats, which were i.c.v. pre-treated with: (1) saline (control), (2) L-arginine (L-Arg), to increase the availability of substrate for NO biosynthesis, (3) D-arginine (D-Arg), (4) 3-[4-morpholinyl]-sydnonimine-hydrochloride (SIN-1), an NO donor, or (5) CaCl2, a cofactor of brain calcium-calmodulin-dependent cNOS(I). In additional experiments, the levels of L-citrulline (the stable equimolar product derived from enzymatic cleavage of L-Arg by NO synthase) were determined in the brain of vehicle- or cadmium-treated rats. 3. The pressor response to cadmium reached its nadir at 5 min (43+/-4 mmHg) and lasted over 20 min in controls. L-Citrulline/protein content was reduced from 35 up to 50% in the cerebral cortex, pons, hippocampus, striatus, hypothalamus (P<0.01) of cadmium-treated rats compared with controls. Central injection of N(G) nitro-L-arginine-methylester (L-NAME) also reduced the levels of L-citrulline in the brain. 4. Both the magnitude and duration of the response were attenuated by 1.21 and 2.42 micromol SIN-1 (32+/-3 and 15+/-4 mmHg, P<0.05), or 1 micromol CaCl2 (6+/-4 mmHg, P<0.05). Selectivity of action exerted by SIN-1 was confirmed by the use of another NO donor, S-nitroso-N-acetyl-penicillamine (SNAP). Both L-Arg and D-Arg caused a mild but significant attenuation in the main phase of the pressor response evoked by cadmium. However, only L-Arg reduced the magnitude of the delayed, pressor response. Despite their similarity in ability to attenuate the cadmium-induced pressure effect, L-Arg and its isomer exerted differential biochemical changes in brain L-citrulline, as L-Arg normalized cadmium-induced reduction in L-citrulline levels, whereas i.c.v. D-Arg did not. 5. We conclude that the pressor effect of i.c.v. cadmium is due, at least in part, to reduced NO formation, consequent to inhibition of brain NO synthase. Accumulation of cadmium in the central nervous system could interfere with central mechanisms (including NO synthase) implicated in the regulation of cardiovascular function.

Chronic kinin receptor blockade induces hypertension in deoxycorticosterone-treated rats.

1. The contribution of endogenous kinins to the regulation of blood pressure and renal function of Wistar rats was evaluated by use of the new B2-receptor antagonist, Hoe 140, (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin). 2. Neither Hoe 140 (4 micrograms h-1 s.c., for 6 weeks), nor vehicle altered systolic blood pressure (SBP, tail-cuff plethysmography) or renal function in rats, under normal conditions. 3. Chronic administration of deoxycorticosterone (DOC, 25 mg kg-1 s.c., weekly) increased SBP slightly only after 6 weeks (from 124 +/- 2 to 133 +/- 3 mmHg, P < 0.05). An earlier and greater rise in SBP (P < 0.01) occurred when DOC was combined with chronic infusion of Hoe 140 (from 125 +/- 1 to 154 +/- 3, P < 0.01). The hypertensive effect of Hoe 140 was confirmed by direct measurement of mean blood pressure (143 +/- 2 vs 122 +/- 2 mmHg in controls, P < 0.01). 4. DOC caused an initial fall, followed by a transitory increase in urinary volume and sodium excretion; thereafter, both parameters returned to baseline. The initial antidiuretic and antinatriuretic effects were enhanced by Hoe 140 (P < 0.05). 5. Urinary prostaglandin E2 excretion was increased by DOC (from 106 +/- 3 to 153 +/- 4 ng 24 h-1, P < 0.01) and this effect was prevented by Hoe 140 (from 95 +/- 3 to 104 +/- 3 ng 24 h-1, NS). By contrast, the high urinary vasopressin excretion and suppressed plasma renin activity found in DOC-treated rats were not altered by Hoe 140. 6. These data suggest that endogenous kinins play an important role in the regulation of arterial blood pressure under conditions of mineralocorticoid excess.

Prevention by blockade of angiotensin subtype1-receptors of the development of genetic hypertension but not its heritability.

1. We determined whether early inhibition of angiotensin II subtype1 (AT1) receptors by the newly synthesized nonpeptidic antagonist, A-81988, can attenuate the development of hypertension in spontaneously hypertensive rats (SHR) and if the altered blood pressure phenotype can be passed on to the subsequent generation, not exposed to the antagonist. 2. Pairs of SHR were mated while drinking tap water or A-81988 in tap water, and the progeny was maintained on the parental regimen until 14 weeks of age. At this stage, A-81988-treated rats showed lower systolic blood pressure and body weight values (136 +/- 5 versus 185 +/- 4 mmHg and 247 +/- 4 versus 283 +/- 4 g in controls, P < 0.01); while heart rate was similar. In addition, mean blood pressure was reduced (101 +/- 7 versus 170 +/- 7 mmHg in controls, P < 0.01), and the pressor responses to intravenous or intracerebroventricular angiotensin II were inhibited by 27 and 59%, respectively. Heart/body weight ratio was smaller in A-81988-treated rats (3.2 +/- 0.1 versus 3.8 +/- 0.1 in controls, P < 0.01). 3. The antihypertensive and antihypertrophic effect of A-81988 persisted in rats removed from therapy for 7 weeks (systolic blood pressure: 173 +/- 4 versus 220 +/- 4 mmHg, heart/body weight ratio: 3.4 +/- 0.1 versus 4.1 +/- 0.1 in controls at 21 weeks of age, P < 0.01 for both comparisons), whereas the cardiovascular hypertensive phenotype was fully expressed in the subsequent generation that was maintained without treatment. 4. These results indicate that chronic blockade of angiotensin AT1-receptors attenuates the development of hypertension in SHR but it does not prevent the transmission of hypertension to the following generation. Thus, heritability of the SHR's hypertensive trait is not affected by pharmacological manipulation of the cardiovascular phenotype.

Regulation of bradykinin B2-receptor expression by oestrogen.

1. Tissue kallikrein is overexpressed in the kidney of female rats, this sexual dimorphism being associated with a greater effect of early blockade of bradykinin B2-receptors on female blood pressure phenotype. We evaluated the effect of ovariectomy and oestradiol benzoate (50 micrograms kg-1 every two days for two weeks) on the vasodepressor response to intra-arterial injection of bradykinin (150-900 ng kg-1) and on the expression of bradykinin B2-receptors. 2. Ovariectomy reduced the magnitude of the vasodepressor response to bradykinin and unmasked a secondary vasopressor effect. Oestrogen replacement restored the vasodepressor response to bradykinin in ovariectomized rats. 3. The vasodepressor responses to sodium nitroprusside (3-18 micrograms kg-1), acetylcholine (30-600 ng kg-1), desArg9-bradykinin (150-900 ng kg-1) or prostaglandin E2 (30-600 ng kg-1) were significantly reduced by ovariectomy. Oestrogen restored to normal the responses to desArg9-bradykinin, acetylcholine and prostaglandin E2, but not that to sodium nitroprusside. 4. B2-receptor mRNA levels were decreased by ovariectomy in the aorta and kidney and they were restored to normal levels by oestrogen. Neither ovariectomy nor oestradiol affected receptor expression in the heart and uterus. 5. These results indicate that oestrogen regulates B2-receptor gene expression and function. Since kinins exert a cardiovascular protective action, reduction in their vasodilator activity after menopause might contribute to the increased risk of pathological cardiovascular events. Conversely, the cardioprotective effects of oestrogen replacement might be, at least in part, mediated by activation of the kallikrein-kinin system.

Effects of Hoe 140, a bradykinin B2-receptor antagonist, on renal function in conscious normotensive rats.

1. The present study was designed to determine if endogenous kinins are involved in the regulation of arterial blood pressure and renal function in conscious rats given deoxycorticosterone enantate (DOC, 25 mg kg-1, s.c., weekly) or vehicle for two weeks. 2. The bradykinin B2-receptor antagonist, D-Arg[Hyp3,Thi5,D-Tic7,Oic8]- bradykinin (Hoe 140), at a dose of 300 micrograms kg-1, s.c., blocked the hypotensive effect of 300 ng kg-1 bradykinin i.a., but it did not alter the blood pressure lowering action of 300 ng kg-1 acetylcholine or prostaglandin E2. Inhibition of the response to bradykinin persisted up to 6 h after the administration of Hoe 140. 3. Administration of 300 micrograms kg-1 Hoe 140 s.c. four times a day did not alter mean blood pressure, renal blood flow, or renal function in rats given DOC-vehicle. However, it decreased urinary volume by 70% (from 48.2 +/- 3.8 to 14.3 +/- 3.7 ml 24 h-1, P less than 0.01) and urinary secretion of sodium by 54% (from 1.02 +/- 0.05 to 0.47 +/- 0.16 mmol 24 h-1, P less than 0.01) and potassium by 30% (from 2.93 +/- 0.15 to 2.04 +/- 0.15 mmol 24 h-1, P less than 0.05) in DOC-treated rats. Mean blood pressure, glomerular filtration rate and total renal blood flow remained unchanged. 4. Our results suggest that endogenous kinins play a role in the regulation of renal excretion of water and sodium in the presence of elevated levels of DOC.

Verapamil prevents the acute hypertensive response to intracerebroventricular cadmium in conscious normotensive rats.

Cadmium, a trace element from natural and industrial sources, may contribute to the pathogenesis of arterial hypertension. We evaluated the effect induced by acute intracerebroventricular (icv) administration of cadmium on mean blood pressure of normotensive conscious rats. Intracerebroventricular cadmium (1 to 10 micrograms) produced a dose-dependent, sustained increase in mean blood pressure. The hypertensive response to icv cadmium was significantly (P < .01) prevented by icv pretreatment with verapamil (10 to 100 micrograms). A preventive effect was exerted also by icv nifedipine (100 micrograms); however, this result was attributable, at least in part, to the antihypertensive action of the vehicle, polyethylene glycol. The hypertensive response to icv cadmium was blunted by icv administration of 10 ng clonidine, 10 micrograms vasopressin antagonist, or 10 micrograms bradykinin antagonist (P < .05), but it was not altered by icv enalaprilat (100 micrograms). These results indicate that brain calcium channels play a role in the hypertensive action induced by icv cadmium. Accumulation of cadmium in the brain caused by prolonged exposure to this heavy metal might lead to chronic arterial hypertension.

Chronic inhibition of bradykinin receptors alters cardiovascular function in rats with an excess of circulating vasoconstrictors.

1. The contribution of endogenous kinins to the regulation of blood pressure of angiotensin-treated rats was evaluated using the new bradykinin B2-receptor antagonist Hoe 140 (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin). 2. Chronic intraperitoneal infusion of 20 nmol/day angiotensin II did not alter systolic blood pressure or plasma angiotensin II levels. A significant increase in plasma aldosterone and corticosterone levels was observed after 4 weeks (from 89 +/- 20 to 140 +/- 22 and from 147 +/- 30 to 225 +/- 33 pg/ml, respectively; P < 0.05). 3. Combined administration of 20 nmol/day angiotensin II and 75 nmol Hoe 140 induced a significant increase in systolic blood pressure from 126 +/- 3 to 142 +/- 3 and 137 +/- 3 mmHg, at 1 and 4 weeks, respectively (P < 0.05). This effect was not accompanied by significant changes in plasma angiotensin II concentration. The angiotensin-induced increase in plasma levels of aldosterone and corticosterone was not altered by the antagonist Hoe 140. 4. These findings indicate that blockade of endogenous kinin receptors enhances the slow pressor effect induced by angiotensin II. Therefore, endogenous kinins may play a role in preventing the cardiovascular effects of an excess of vasoconstrictors.

Amides and formamidines with antinociceptive activity (note II).

Forty amides, formamidines and trifluoromethylsulfonylamides bearing on the nitrogen a cyclohexyl residue, eventually 2-substituted, were prepared and tested for analgesic activity against a chemical stimulus. Good activity was exhibited by amides 9, 11 and 28, by formamidine 34, as well as by triflyamide 40. Eleven additional compounds exhibited a moderate activity.

Quinoxaline chemistry. Part 6--Synthesis and evaluation of antiulcer and gastroprotective activity of 2-[arylmethylmercapto-, arylmethylsulfinyl-, piperazinyl-3-R-substituted]quinoxalines.

Thirty compounds possessing quinoxaline structure bearing either substituted arylmethylmercapto-, arylmethylsulfinyl group or a piperazinyl moiety in position 2 were prepared in order to evaluate an antiulcer and gastroprotective activity in rat pylorus ligature, in comparison with omeprazole and ranitidine at the dose of 100 mg/kg after oral administration. Among the compounds of the first group one third showed a moderate activity being about half potent as omeprazole whereas in the second group compound 5b exibited an activity superior to that of ranitidine accompanied with the lowest incidence of lesions and mortality and another compound (5i) was equiactive as ranitidine.

Synthesis and evaluation of gastroprotective and antiulcer activity of some 2-substituted-1H-imidazo[4,5-b] pyridines and -1H-benzimidazoles.

Several compounds possessing imidazo[4,5-b]pyridine and benzimidazole structure bearing substituents in position 2 were prepared in order to evaluate an anti-ulcer and gastroprotective activity in rat pylorus ligature, in comparison with omeprazole. Among sixteen compounds taken as representatives of the synthetised series only one (3d) showed a good activity by i.m. administration at 50 mg/kg, while by oral administration of 100 mg/kg a certain number was active and in some cases this activity was quite superior to that of omeprazole.