Student insights towards animal welfare science and law. Survey results from Sassari University, Italy

In this paper, we describe the results of an online survey consisting of 23 questions created to evaluate the knowledge and interest on animal welfare by students attending 15 different scientific, medical, and biomedical courses at University of Sassari, Italy. The survey collected students' demographic data, level of knowledge both on animal welfare and 3Rs, as well as their opinions on animal experimentation. The majority of the cohort was female and over 24 years of age. About a third of the students responded that their graduate programme included subjects that taught science, ethics, and animal welfare legislation. Just 21.2% of respondents had heard about the concept of 3Rs. About a quarter of the students believed that animal models can be replaced by in vitro and in silico methods while half believed that both are needed. However, 70% of the participants did not know the existence of an Ethics and Animal Welfare Committee. The result showed the importance of an Animal Welfare Course for the professional future of a larger number of students and underlined the key role of veterinary medicine in promoting ethics and animal experimentation.

An Overview of Antibiotics as Emerging Contaminants: Occurrence in Bivalves as Biomonitoring Organisms

Simple Summary

In recent years, the use of antibiotics has increased worldwide in both human and veterinary fields. This led to them accumulating in the environment to such an extent that they are actually included in the category of contaminants of emerging concern. For this reason, many of them have been included in monitoring lists of potential pollutants by competent authorities in order to limit their concentration in surface waters and to determine the risk to the aquatic environments. From this perspective, the aim of this review is to update and discuss the available data on antibiotic residues, using bivalves as biomonitoring organisms. Bivalves are good candidate for this purpose, being globally present in large and accessible populations, sedentary and able to accumulate several xenobiotics thanks to their large filtration capacity. The current research indicates that antibiotics’ presence in bivalves has been investigated along European, American and Asian coasts. Except for tetracycline, determined at high concentration in the North Adriatic Sea, all antibiotics residues in bivalves were under the maximum residual limit established by the competent authorities. Nevertheless, further investigations are necessary in order to prevent antimicrobial resistance, preserve the environment from antibiotic pollution and monitor the associated risk for animals and humans.

Abstract

Antibiotics are used for therapeutic and prophylactic purposes in both human and veterinary medicine and as growth promoting agents in farms and aquaculture. They can accumulate in environmental matrices and in the food chain, causing adverse effects in humans and animals including the development of antibiotic resistance. This review aims to update and discuss the available data on antibiotic residues, using bivalves as biomonitoring organisms. The current research indicates that antibiotics’ presence in bivalves has been investigated along European, American and Asian coasts, with the majority of studies reported for the last. Several classes of antibiotics have been detected, with a higher frequency of detection reported for macrolides, sulfonamides and quinolones. The highest concentration was instead reported for tetracyclines in bivalves collected in the North Adriatic Sea. Only oxytetracycline levels detected in this latter site exceeded the maximum residual limit established by the competent authorities. Moreover, the risk that can be derived from bivalve consumption, calculated considering the highest concentrations of antibiotics residues reported in the analyzed studies, is actually negligible. Nevertheless, further supervisions are needed in order to preserve the environment from antibiotic pollution, prevent the development of antimicrobial resistance and reduce the health risk derived from seafood consumption.

Different response of intracerebroventricular cadmium administration on blood pressure in normal and low urinary kallikrein rats

Cadmium intracerebroventricular (i.c.v.) administration, at definite concentrations, induces a dose-dependent increase in the systemic blood pressure. Kallikreins are suggested to be important regulators of cardiovascular function. We evaluated the effects of 10 microg i.c.v. cadmium on mean blood pressure (MBP) and several urinary parameters such as 24h urine volume, sodium and potassium excretion and osmolality in a rat strain inbred for low urinary kallikrein and in normal-kallikrein Wistar rats. Low-kallikrein rats (LKR) showed an increase in MBP that, after an initial peak (27% from baseline), persisted higher than basal levels (10%) over 24h. In normal-kallikrein rats (NKR) a different reaction of blood pressure to cadmium was observed, causing a temporary increase (26% from baseline) of the systemic blood pressure, that returned to normal values within 2h. In addition, LKR showed a considerable reduction in the urinary volume (UV; 43.0+/-20 ml/24h versus 13.2+/-6 ml/24h, P<0.006), with an increase in the urinary osmolality (U(Osm); 500+/-210 mOsm/l versus 1391+/-245 mOsm/l, P<0.0002). Sodium (U(Na); 1761+/-432 microEq/24h versus 1156+/-522 microEq/24h, P<0.03) and potassium excretion (U(K); 2186+/-482 microEq/24h versus 936+/-299 microEq/24h, P<0.0006) were both significantly reduced. No changes in UV, U(Osm) and U(K) were observed in normal urinary kallikrein rats with the exception of U(Na) excretion that was significantly increased (667+/-274 microEq/24h versus 1725+/-300 microEq/24h, P<0.03). These results suggest that a genetically determined defect in urinary kallikrein excretion leads to a different hypertensive response to i.c.v. cadmium and to a different renal excretion of electrolytes. Perhaps the differences of blood pressure response could be due, at least in part, to a different sensitivity of LKR to cadmium: this implies a complex and articulate hypertensive effect of cadmium involving more systems than those supposed so far.

Relationship between cerebrospinal fluid pressure and plasmatic ADH

In a healthy human being, the extracellular volume is kept constant by homeostatic systems. One of these is represented by the antidiuretic hormone (ADH). ADH release is modulated by osmoreceptors and baroreceptors which respond to an increase in osmolality of extracellular fluid and a decrease in blood volume, respectively. In previous studies we investigated the existence of additional structures sensitive to plasma volume modifications. We found evidence of the presence of such receptors in the inner ear, with nervous connections to supraoptic and paraventricular nuclei. However, the possibility that the cerebral ventricle wall contained stretch sensors could not be excluded. To test our hypothesis, we studied 19 rats divided into three groups: Group 1 (n =7), Group 2 (n =7) and Group 3 (control group n =5). In each rat, under total anaesthesia, a femoral cannula was inserted into the left artery and a 22 gauge stainless steel cannula was implanted into the left cerebral ventricle. In the first group an isotonic fluid, similar to the animal's cerebrospinal fluid (CSF), was infused intracerebroventricularly (ICV) at a rate of 0.6 microl min-1 continuously for 6 h. In the second group, under the same conditions, CSF was aspirated; the third group was used as the control. In all animals, plasma modifications of ADH (pADH), osmolality (pOSM), Na+(pNa+) and K+(pK+) were evaluated before and after the experimental procedures. Mean arterial pressure (MAP) and heart rate (HR) were recorded throughout the experiment. At the end of the experiment no significant changes in pNa+, pK+, MAP and HR were observed. Plasma osmolality was significantly lower in Group 2 before and during the experimental procedure, since we deliberately expanded the volume in animals of Group 2 to partially suppress ADH, in order to evaluate its modifications. Plasma ADH fell in the first experimental group (-37.4%+/-6.3 sem) after the ventricular pressure had been increased, and rose in the second (+47.3%+/-14.7 sem) after ventricular decompression. These changes were statistically significant in comparison with those occurring in control subjects (-0.9+/-18.9 sem;P =0.07 and P =0.03, respectively). These results suggest the presence of additional volume receptors probably located in the cerebral ventricles, capable of controlling ADH. The importance of these receptors in physiological situations of plasma volume contraction or expansion remains to be established.

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.

Cardiovascular phenotype of a mouse strain with disruption of bradykinin B2-receptor gene

BACKGROUND

To evaluate the role of kinins in the regulation of cardiovascular function, we studied the phenotype of a mouse strain with disruption of the bradykinin B2-receptor gene (Bk 2r-/-).

METHODS AND RESULTS

Under basal conditions, tail-cuff blood pressure was higher in Bk2r-/- than in wild-type Bk2r+/+ and heterozygous Bk2r+/- mice (124+/-1 versus 109+/-1 and 111+/-2 mm Hg, respectively; P<.01 for both comparisons), a difference that was confirmed by measurements of intra-arterial blood pressure in unanesthetized mice. Heart weight was greater in Bk2r-/- than in Bk2r+/+ and Bk2r+/- mice (505+/-10 versus 449+/-12 and 477+/-10 mg/100 g body wt, P<.05). Chronic blockade of B2-receptors by Icatibant (50 nmol/100 g body wt twice a day S.C.) or inhibition of nitric oxide synthase by nitro-L-arginine-methyl ester (0.14 mmol/100 g body wt orally) increased the blood pressure of Bk2r+/+ to the levels of Bk2r-/- mice. Compared with the wild-type strain, both Bk2r-/- and Bk2r+/- mice showed exaggerated vasopressor responses to angiotensin II. In addition, chronic administration of an angiotensin AT1-receptor antagonist reduced the basal blood pressure of Bk2r-/- by 21+/-3 mmHg (P<.05) to the levels of Bk2r+/+. No difference was detected between strains as far as plasma renin activity and the expression of renin and AT1-receptor genes are concerned. Chronic salt loading (0.84 mmol/g chow for 15 days) increased the blood pressure of Bk2r-/- and Bk2r+/- by 34+/-3 and 14+/-6 mm Hg, respectively, whereas it was ineffective in Bk2r+/+.

CONCLUSIONS

Our results suggest that a normally functioning B2-receptor is essential for the maintenance of cardiovascular homeostasis in mice. Dysfunction of the kallikrein-kinin system could contribute to increase blood pressure levels by leaving the activity of vasoconstrictor agents unbalanced.

Effect of atrazine administration on spontaneous and evoked cerebellar activity in the rat

The effect of atrazine oral administration on cerebellar forelimb projection area was studied in rats in vivo. Rats acutely treated with atrazine (100 mg kg-1, BW) showed a significant decrease in spontaneous Purkinje cell firing rate. Atrazine also decreased the cerebellar potentials evoked by electrical stimulation of the ipsilateral radial nerve, affecting mostly the response to climbing fiber input. These results demonstrate that atrazine exerts a toxic action on central nervous system. The effects on the cerebellar somatosensory cortex could be responsible for motor disorders frequently observed in animals intoxicated with atrazine.

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.

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.

Metabolic and renal effects of Laevo-carnitine and propionyl-carnitine in rats with subtotal nephrectomy

The renal and metabolic effects of chronic carnitine administration were evaluated in the early stages of experimentally-induced renal failure. Laevo-carnitine (n = 5), Propionyl-carnitine (n = 5) both at 200 mg kg-1 of body weight, or vehicle (physiological saline solution, 0.4 ml kg-1 body weight, n = 5) were administered daily for 3 days prior to 2/3 nephrectomy and for 25 days thereafter, by intraperitoneal route. At the end of the experiment, no significant differences were found in systolic blood pressure and heart rate among groups. During the 25 days after nephrectomy, body weight increased by 71 +/- 13 g in the control group and by 50 +/- 26 g and 42 +/- 9 g in Laevo-carnitine and Propionyl-carnitine groups, respectively (P < 0.05 vs control for both comparisons). Urinary sodium excretion was increased in carnitine-treated rats (Laevo-carnitine: from 1.03 +/- 0.3 to 1.36 +/- 0.3 mEq day-1, Propionyl-carnitine: from 1.2 +/- 0.2 to 1.66 +/- 0.2 mEq day-1, P < 0.05 for both comparisons), but not in those given vehicle. Twenty-five days after nephrectomy, plasma creatinine was lower in carnitine-treated rats (Laevo-carnitine: 0.98 +/- 0.12 mg dl-1, Propionyl-carnitine: 1.06 +/- 0.15, vehicle: 1.52 +/- 0.09, P < 0.05 vs control for both comparisons). Plasma triglycerides and VLDL were decreased by nephrectomy and this effect was prevented by carnitine treatment. The data indicate that the carnitine blunts the increase in plasma creatinine that occurs early after partial nephrectomy and normalizes the plasma lipoprotein pattern. Thus, carnitine might protect against the development of renal failure in this experimental model.

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.

Intracranial volume receptors: possible role on ADH homeostatic control

Volume receptors are situated in many organs and are capable of modulating ADH secretion. We have evaluated the variation of plasma ADH concentration after an experimentally induced increase of cerebrospinal fluid (CSF) pressure (PCSF). The experiment was performed in controlled environmental conditions to avoid pain or stress-related ADH release. In 15 rats (10 experimental, 5 control) a cannula was positioned in the left cerebral ventricle: in the experimental group artificial CSF was infused at a rate of 0.6 (microliter/min for 6h: this manoeuvre, in a separate set of animals obtained an increase from 13.03 +/- 0.8 to 25.4 +/- 2.5 cmH2O of PCSF. The same conditions were reproduced in the control group without infusion into lateral ventricle. At the end of the experiment, plasma ADH had fallen significantly in the experimental group from 18.9 +/- 4.8 to 11.9 +/- 2.3 pg/ml (p < 0.05), while it was not changed in the control group (from 25.5 +/- 13.7 to 23.7 +/- 16.2 pg/ml). Heart rate, arterial pressure, plasma Na+ and osmolality, did not change significantly. Plasma K+ fell significantly in both groups: from 5.5 +/- 0.6 to 4.3 +/- 0.3 (p < 0.05) and from 5.4 +/- 0.7 to 4.3 +/- 0.15 mEq/l (p < 0.05) in the experimental and control group respectively. Plasma creatinine was normal, checked only at the end of the experiment. Our results demonstrate that a relationship exists between PCSF variations and plasma ADH concentration. We believe this relationship is due to the pressure receptors in the cerebral ventricles or in structures connected to it, such as the inner ear, and we hypothesize the existence of a control system of body fluids, more diffused than though to be, up till now.

Blood pressure sensitivity to salt in rats with low urinary kallikrein excretion

We evaluated if a rat strain inbred for reduced urinary kallikrein excretion differs from normal-kallikrein Wistar rats regarding blood pressure in basal conditions and during alterations in sodium balance. Low-kallikrein rats showed greater systolic blood pressure values (125 +/- 3 vs. 114 +/- 2 mmHg in controls, P < 0.01) at 9 weeks of age. Systolic blood pressure was increased after 20 days of dietary sodium loading in the low-kallikrein group and remained unchanged in controls (150 +/- 6 vs. 112 +/- 2 mmHg, P < 0.01) and this effect was associated with a reduced cumulative excretion of sodium (23% less in the low-kallikrein group compared with controls, P < 0.01). Urinary creatinine excretion was decreased by sodium loading in both groups, and this effect was more pronounced in the low-kallikrein group. The group-difference in urinary kallikrein excretion found in basal conditions (2.49 +/- 0.10 vs. 7.78 +/- 0.53 Pkat/100 g body weight, P < 0.01) was enhanced by high salt diet (1.05 +/- 0.21 vs. 8.31 +/- 0.70 Pkat/100 g body weight, P < 0.01). The ratio of heart weight to body weight was significantly greater in low-kallikrein rats (331 +/- 7 vs. 275 +/- 4 mg/100 g body weight, P < 0.01), whereas the ratio of kidney weight to body weight was lower (329 +/- 5 vs. 370 +/- 8 mg/100 body weight, P < 0.01). Our results indicate that a genetically-determined defect in urinary kallikrein excretion is associated with a greater blood pressure sensitivity to salt, possibly due to altered renal sodium handling.

Urinary kallikrein: a marker of blood pressure sensitivity to salt

We evaluated if a rat strain inbred for low urinary kallikrein excretion differs from normal-kallikrein Wistar rats regarding blood pressure levels in basal conditions and during alterations in sodium balance. Blood pressure was measured in unanesthetized rats on normal sodium intake. Then, blood pressure sensitivity to salt was evaluated over a period of 20 days of high sodium diet (0.84 mmol per g chow). Low-kallikrein rats showed greater systolic blood pressure levels (125 +/- 3 vs. 114 +/- 2 mm Hg in controls, P < 0.01) at nine weeks of age. Systolic blood pressure was increased after sodium loading in the low-kallikrein group and remained unchanged in controls (150 +/- 6 vs. 112 +/- 2 mm Hg, P < 0.01). This effect was associated with a reduced cumulative urinary excretion of sodium in the low-kallikrein rats. No group difference was found in the clearance of endogenous creatinine in basal conditions. Urinary creatinine excretion decreased during sodium loading, particularly in the low-kallikrein group. The group-difference in urinary kallikrein excretion found in basal conditions (6.85 +/- 0.31 vs. 20.74 +/- 1.71 nkat/24 hr in controls, P < 0.01) was enhanced by high salt diet (2.96 +/- 0.67 vs. 22.07 +/- 2.47 nkat/24 hr in controls, P < 0.01). In addition, renal kallikrein activity and content were reduced in low-kallikrein rats. The latter group showed a greater ratio of heart weight to body wt both in basal conditions and after sodium loading. The ratio of kidney weight to body wt was reduced after sodium loading. These results indicate that a genetically-determined defect in urinary kallikrein excretion is associated with a greater blood pressure sensitivity to salt, possibly due to altered renal sodium handling.

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.

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)

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)

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.

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)

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)

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)

Synthesis and evaluation of gastroprotective activity of omeprazole related benzimidazole, imidazo[4,5-b]pyridine and quinoxaline 2-substituted derivatives

Twenty compounds possessing benzimidazole, imidazo[4,5-b]pyridine and quinoxaline structure bearing either a substituted arylmethylmercapto- or an arylmethylsulfinyl group in position 2 were prepared in order to evaluate an antiulcer and gastroprotective activity in rat pylorus ligature, in comparison with omeprazole at the dose of 50 mg/kg after i.m. administration. One third of these compounds showed a moderate activity, being about half potent as omeprazole.

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.

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.

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.

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.

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.

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.

Role of brain kallikrein-kinin system in regulation of adrenocorticotropin release

We evaluated whether the brain kallikrein-kinin system plays a role in the regulation of adrenocorticotropin (ACTH) release in rats. Intracerebroventricular (icv) injection of bradykinin (0.24 nmol) increased plasma immunoreactive ACTH (irACTH) levels (from 93 +/- 4 to 200 +/- 12 pg/ml, P less than 0.01). This effect was prevented by icv kinin antagonist at 15.4 nmol/h (from 98 +/- 5 to 108 +/- 6 pg/ml; not significant). The antagonist did not alter the increase in plasma irACTH levels induced by icv corticotropin-releasing factor (CRF), arginine vasopressin, or prostaglandin E2. Melittin (7 nmol/h icv) increased plasma irACTH from 95 +/- 4 to 268 +/- 7 pg/ml (P less than 0.01). This effect was prevented by icv kinin antagonist (15.4 nmol/h), kallikrein antibodies (13 pmol/h), or indomethacin (0.28 mmol/h). ACTH response to melittin was not altered by antagonists of CRF or vasopressin. Intra-arterial injection of insulin (0.3 IU/kg body wt) reduced plasma glucose levels to a similar extent in rats given icv kinin antagonist or vehicle; the ACTH response to insulin-induced hypoglycemia was slightly less in rats given kinin antagonist than in those given vehicle (55 +/- 5 vs. 86 +/- 4 pg/ml, P less than 0.05). The brain kallikrein-kinin system may play a role in the regulation of ACTH secretion in stimulated conditions.

Endothelin-1-induced renal vasoconstriction is blunted by enalaprilat and enhanced by EDRF antagonist in awake normotensive rats

We attempt to elucidate the putative indirect mechanisms by which endothelin-1 affects mean blood pressure and renal blood flow in normotensive awake rats. Endothelin-1 (700 pg/kg, i.v.) induced a short-lasting decrease followed by a prolonged increase in mean blood pressure (from 113 +/- 4 to 92 +/- 4 mmHg at 30 sec, 132 +/- 7 mmHg at 10 min, and 129 +/- 6 mmHg at 30 min, p less than 0.01), and caused a profound and long-lasting fall in renal blood flow as measured by Doppler flowmeter technique (from 2.87 +/- 0.29 to 1.40 +/- 0.37 kHz at 30 sec, 1.77 +/- 0.32 kHz at 10 min and 2.10 +/- 0.45 kHz at 30 min, p less than 0.01). Neither the receptor antagonist of bradykinin D-Arg0-Hyp3-Thi5,8-DPhe7-bradykinin (30 micrograms/kg/min, i.v.) nor the antagonist of angiotensin II Sar1, Thr8-angiotensin II (4 micrograms/kg/min, i.v.) altered the changes in mean blood pressure and renal blood flow induced by endothelin-1. The antagonist of EDRF synthesis, NG-monomethyl-L-arginine (100 micrograms/kg/min, i.v.) enhanced the endothelin-1-induced increase in mean blood pressure (endothelin-1: 20 +/- 2 mmHg vs endothelin-1 + EDRF antagonist: 39 +/- 3 mmHg at 10 min, p less than 0.01) and decrease in renal blodo flow (endothelin-1: -40 +/- 4% vs endothelin-1 + EDRF antagonist: -73 +/- 3% at 10 min, p less than 0.01).2+ mediated by the blockade of angiotensin II formation.

Efficacy of nifedipine to prevent systemic and renal vasoconstrictor effects of endothelin

We investigated whether systemic and renal vasoconstriction induced by porcine endothelin (endothelin 1) is prevented by nifedipine in awake normotensive rats. Endothelin (0.07-1.4 nmol/kg iv) induced a long-lasting increase in mean blood pressure (MBP) and a decrease in renal blood flow (RBF). Maximal decrease in RBF was 25 +/- 7% (0.07 nmol/kg), 40 +/- 2 (0.35), 67 +/- 5 (0.70), and 74 +/- 8 (1.4). Hemodynamic parameters were back to base line within 35 +/- 5 min (0.07 nmol/kg), 43 +/- 6 (0.35), 60 +/- 4 (0.70), and 81 +/- 7 (1.4). Intravenous bolus injection of either angiotensin II (ANG II, 0.006-0.024 nmol/kg) or norepinephrine (0.40-1.60 nmol/kg) caused a dose-related short-lasting increase in MBP and a decrease in RBF. Endothelin was less potent than ANG II (1:3.42) and more potent than norepinephrine (1:0.015) as a renal vasoconstrictor. Nifedipine (1 mg/kg ip) was equally effective in preventing the increase in MBP caused by endothelin, norepinephrine, or ANG II. It exerted a weaker protection on the renal hemodynamic response to endothelin compared with the inhibition of the other two vasoconstrictors. Thus the regression line representing the relationship between endothelin-induced changes in MBP and RBF was steeper in rats given nifedipine (slope: vehicle, -1.33; nifedipine, -5.50; P less than 0.05). These studies suggest that nifedipine can partially prevent systemic and renal vasoconstriction caused by exogenously administered endothelin in awake normotensive rats.

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.

Effect of endothelin on regional hemodynamics and renal function in awake normotensive rats

The effects of endothelin on regional hemodynamics and renal function were studied in awake normotensive rats. Intravenous injection of endothelin (700 pmol/kg) transiently lowered mean blood pressure (from 108 +/- 2 to 84 +/- 2 mm Hg, p less than 0.01), due to a reduction in total vascular resistance (38 +/- 1%, p less than 0.01), and increased stroke volume (29 +/- 5%, p less than 0.01) and heart rate (from 399 +/- 18 to 447 +/- 18 bpm, p less than 0.05); mesenteric and renal blood flow was reduced (37 +/- 13, p less than 0.05 and 63 +/- 5%, p less than 0.01), whereas carotid blood flow was increased (78 +/- 5%, p less than 0.01). This effect was followed by long-lasting hypertension due to increased total vascular resistance (112 +/- 19%, p less than 0.01); stroke volume, mesenteric, and renal blood flow were reduced (34 +/- 5, 41 +/- 4, and 58 +/- 4%, respectively, p less than 0.05) and carotid blood flow returned to basal levels. Bilateral nephrectomy enhanced the initial hypotensive effect. Pretreatment with nifedipine blocked the hypertensive effect, whereas bilateral nephrectomy did not. A subpressor dose of endothelin (70 pmol/kg) had no effect on stroke volume, mesenteric blood flow, glomerular filtration rate, and plasma renin activity; carotid blood flow was transiently increased (48 +/- 16%, p less than 0.05), then returned to basal levels; renal blood flow decreased (22 +/- 6 and 15 +/- 4% at 30 s and 10 min, respectively p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)