This report documents an incidental finding during a study investigating the effects of melatonin supplementation on the development of blood pressure in SHR. Administration of 10 mg/kg/day of melatonin in drinking water during pregnancy to Wistar-Kyoto (WKY) dams caused a loss of more than 50% of the pups by the age of three weeks and 95% by the age of 6 weeks. There was no maternal morbidity or mortality in the two strains or death of any of the SHR pups. No obvious physical defects were present but mean body weight was lower in the surviving WKY rats when compared to that of melatonin supplemented SHR or non-supplemented WKY pups. The reason for the high mortality in WKY pups is uncertain and appears to be strain if not batch specific. There is a need for caution in its use, particularly during pregnancy, and clearly necessitates more detailed studies.
This study examined whether alpha1B-adrenoceptors are involved in mediating adrenergically-induced renal vasoconstrictor responses in rats with pathophysiological and normal physiological states.
The present investigation was aimed at evaluating the cardiac and total plasma kininogen levels, as well as LVWT in hypertensive and diabetic rats. STZ-induced diabetes produced a significant (P < 0.001) rise in mean arterial blood pressure (BP). The LVWT increased (P < 0.001) in SHR with and without diabetes) and diabetic WKYR. The cardiac tissue, as well as total plasma kininogen levels fell significantly (P < 0.001) in diabetic WKYR and SHR with and without diabetes compared to the control WKYR. These findings suggest that reduced kininogen levels may indicate a deficiency in kinin generation in the heart and in the peripheral circulation in diabetic and hypertensive rats. This effect may contribute to the development of LVH.
Oil palm (Elaeis guineensis) leaf extract (OPLE) possesses good ex vivo vasodilation and antioxidant properties. This study evaluated the catechin-rich OPLE antioxidant, antihypertensive, and cardiovascular effects in normal and nitric oxide (NO)-deficient hypertensive rats. OPLE was administered orally (500 mg/kg of body weight/day) to normotensive Wistar rats and N(ω)-nitro-L-arginine methyl ester (L-NAME)-induced NO-deficient hypertensive rats. OPLE significantly (P
Oxidative stress is involved in the pathogenesis of a number of diseases including hypertension and renal failure. There is enhanced expression of nicotinamide adenine dinucleotide (NADPH oxidase) and therefore production of hydrogen peroxide (H2O2) during renal disease progression. This study investigated the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on Cyclosporine A (CsA) nephrotoxicity in Wistar-Kyoto rats. Rats received CsA (25mg/kg/day via gavage) and were assigned to vehicle, apocynin (2.5mmol/L p.o.), catalase (10,000U/kg/day i.p.) or apocynin plus catalase for 14 days. Renal functional and hemodynamic parameters were measured every week, and kidneys were harvested at the end of the study for histological and NADPH oxidase 4 (NOX4) assessment. Oxidative stress markers and blood urea nitrogen (BUN) were measured. CsA rats had higher plasma malondialdehyde (by 340%) and BUN (by 125%), but lower superoxide dismutase and total antioxidant capacity (by 40%, all P<0.05) compared to control. CsA increased blood pressure (by 46mmHg) and decreased creatinine clearance (by 49%, all P<0.05). Treatment of CsA rats with apocynin, catalase, and their combination decreased blood pressure to near control values (all P<0.05). NOX4 mRNA activity was higher in the renal tissue of CsA rats by approximately 63% (P<0.05) compared to controls but was reduced in apocynin (by 64%), catalase (by 33%) and combined treatment with apocynin and catalase (by 84%) compared to untreated CsA rats. Treatment of CsA rats with apocynin, catalase, and their combination prevented hypertension and restored renal functional parameters and tissue Nox4 expression in this model. NADPH inhibition and H2O2 scavenging is an important therapeutic strategy during CsA nephrotoxicity and hypertension.
Acute exposure to the flavonoid baicalein inhibited endothelium-dependent relaxation in physiological arteries, although the mechanisms are not fully understood. We investigated the effect of baicalein on vascular tone in Wistar-Kyoto (WKY) rat isolated aortic rings in the presence and absence of oxidative stress to further determine the underlying mechanisms. Exposure to baicalein (10 microM) completely abolished endothelium-dependent relaxation induced by acetylcholine and attenuated significantly the endothelium-independent relaxation induced by sodium nitroprusside. Baicalein, similar to Nomega-nitro-L-arginine methyl ester (L-NAME, 10 microM), potentiated significantly the contractile response of aortic rings to alpha1-adrenoceptor agonist phenylephrine. In the presence of L-NAME the baicalein effect on phenylphrine contraction or acetylcholine relaxation was unaltered, suggesting that these effects of baicalein are (like L-NAME effect) endothelial nitric oxide synthase (eNOS)/endothelium-derived nitric oxide-dependent. Inhibition of cyclooxygenase activity with indomethacin (10 microM) or scavenging of superoxide anions with superoxide dismutase (150 units/ml), but not scavenging of hydrogen peroxide with catalase (800 units/ml), enhanced significantly by an essentially similar extent the relaxation to acetylcholine in baicalein-pretreated aortic rings. Relaxant effect to acetylcholine was significantly attenuated in control aortic rings, but was completely abolished in baicalein-pretreated aortic rings in the presence of reduced form of beta-nicotinamide adenine di-nucleotide (beta-NADH, 300 microM). Baicalein blocked beta-NADH (300 microM)-induced transient contractions, suggesting that baicalein may have inhibited activity of NADH/NADPH-oxidase. Baicalein did not alter the failure of acetylcholine to induce relaxation in the presence of pyrogallol (300 microM). In summary, acute exposure to baicalein impairs eNOS/endothelium-derived nitric oxide-mediated vascular tone in rat aortas through the inhibition of endothelium-derived nitric oxide bioavailability coupled to reduced bioactivity of endothelium-derived nitric oxide and to cyclooxygenase-mediated release of superoxide anions.
This study examined the effects of streptozotocin-induced diabetes on blood pressure and cardiac tissue kallikrein levels in WKYR and SHR. Streptozotocin-induced diabetes caused significant (p < 0.001) increase in SBP and DBP in WKYR and SHR as compared with their respective controls. We also observed that the active cardiac tissue kallikrein levels reduced greatly (p < 0.001) in diabetic WKYR and SHR than the normal rats. These findings suggest for the first time that the cardiac tissue kallikrein formation may have a greater role in the regulation of blood pressure and cardiac function.
Intravenous injection of the aspidofractinine alkaloid, kopsingine (1, 0.2-10.0 mg/kg) from Kopsia teoi, produced dose-related decreases in the mean arterial blood pressure and heart rate in anesthetized spontaneously hypertensive rats, which were similar to those seen in normotensive controls. Minor modifications in the molecular structure of kopsingine, as in kopsaporine (2, the 12-demethoxy derivative of kopsingine) and 14,15-dihydrokopsingine (4), did not significantly alter the hypotensive responses, whereas a more drastic change in the structure, as in the heptacyclic kopsidine A (3) and the 3-to-17 oxo-bridged compound 5, resulted in an increase in blood pressure. The antihypertensive effects of kopsingine (1) and its congeners (2 and 4) along with the pressor effects produced by the heptacyclic oxo-bridged compounds (5 and 3) could be ascribed to central as well as peripheral actions.
The mechanism by which insulin causes vasodilatation remains unclear, so we explored this in aortic rings from normal Wistar Kyoto and streptozotocin-induced diabetic rats. Insulin-induced relaxation of phenylephrine-contracted [endothelium (ED) intact or denuded] aortic rings was recorded in the presence or absence of various drug probes. Insulin relaxant effect was more in ED-intact than in-denuded tissues from normal or diabetic rats. l-NAME or methylene blue partially inhibited insulin effect in ED-intact but not the ED-denuded tissues, whereas indomethacin (cyclooxygenase inhibitor) had no effect on any of the tissues, indicating that insulin induces relaxation by ED-dependent and -independent mechanisms, the former via the NOS-cyclic guanosine monophosphate but not the cyclooxygenase pathway. The voltage-dependent K channel (KV) blocker (4-aminopyridine) inhibited insulin action in all the tissues (normal or diabetic, with or without ED), whereas the selective BKCa blocker, tetraethylammonium, inhibited it in normal (ED intact or denuded) but not in diabetic tissues, indicating that KV mediates insulin action in normal and diabetic tissues, whereas the BKCa mediates it only in normal tissues, with possible pathophysiologic absence in diabetic tissues. The inward rectifier K channel (Kir) blocker (barium chloride) significantly inhibited insulin effect only in ED-intact or -denuded diabetic tissues, whereas the KATP channel blocker, glibenclamide, inhibited it only in the ED-denuded diabetic tissues, suggesting that Kir channels mediate insulin-induced relaxation in ED-intact or -denuded diabetic tissues, whereas the KATP channel mediates it in ED-denuded diabetic tissues. All the agents combined did not abolish insulin action, suggestive of a direct vasodilatory effect. In conclusion, insulin causes vasodilatation in normal and diabetic tissues via ED-dependent and -independent mechanisms differentially modulated by K channels, some of which functions are altered in diabetes and thus are potential therapeutic targets.
This study set out to investigate the impact of chronic cumulative blockade of angiotensin II and adrenoceptors in WKY and SHR and to explore how the renovascular responses to adrenergic and angiotensin II receptor agonists may be interdependent. Rats were treated with either losartan, carvedilol or losartan+carvedilol for 7 days and on day eight, animals were pentobarbitone anaesthetized and prepared for renal haemodynamic study. Dose-response relationships were determined in terms of reduction/elevation in the magnitude of renal blood flow in response to intrarenal arterial injection of dopamine, phenylephrine and isoprenaline. Renal vascular responses were blunted in WKY and SHR treated with either losartan or carvedilol as compared to their untreated counterparts (P<0.05). In the combined treated rats, the vascular responses to isoprenaline and phenylephrine were restored to levels observed in the untreated rats, but the renal vasoconstrictor responses to dopamine decreased (P<0.05) in both WKY and SHR. There was a reduction of (P<0.05) in the magnitude of the isoprenaline induced renal vasodilation in all SHR as compared to WKY groups. The data obtained showed that the renal vascular action of dopamine, phenylephrine and isoprenaline depended on an intact renin-angiotensin system (RAS) in WKY and SHR. Treatment with losartan or carvedilol blunted the renal vasoconstrictor/vasodilator responses to sympathomimetics which was attenuated with the combined treatment. These observations using chronic blockade of adrenergic and angiotensin receptors demonstrated that there was a long standing interdependency between the RAS and sympathetic nervous system (SNS) in determining the responsiveness of the renal vasculature of normal and hypertensive rats.
The pathogenesis of cisplatin-induced renal failure is related to reduced renal blood flow due to severe tubular damage and enhanced renovascular resistance. It is also known that alpha(1)-adrenoceptors, the major subtype of alpha-adrenoceptors in renal vasculature play the pivotal role in regulating renal hemodynamics. With this background, we have hypothesized that the altered renal hemodynamics and enhanced renovascular resistance in cisplatin-induced renal failure might be caused by the altered alpha-adrenergic responsiveness with a possible involvement of alpha(1)-adrenoceptors in the renal vasculature. In a unique experimental approach with anesthetized rats, this study has therefore examined if there is any shift in the renovascular responsiveness to renal nerve stimulation and a series of alpha-adrenergic agonists in Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats with cisplatin-induced renal failure in comparison with their body weight-matched normal controls. Thirty-two male rats of both WKY (n=16) and SHR (n=16) origin with body weight 236+/-7.9 g received cisplatin (5mg/kg i.p.). The renal failure was confirmed in terms of significantly reduced renal blood flow, reduced creatinine clearance, increased fractional excretion of sodium, increased kidney index (all P<0.05) and tubular damage. After 7 days of cisplatin, the overnight fasted rats were anesthetized (sodium pentobarbitone, 60 mg/kg i.p.) and renal vasoconstrictor experiments were done. The changes in the vasoconstrictor responses were determined in terms of reductions in renal blood flow caused by electrical renal nerve stimulation or intrarenal administration of noradrenaline, phenylephrine and methoxamine. It was observed that in the cisplatin-treated renal failure WKY and SHR rats there were significant (all P<0.05) reductions in the renal blood flow along with significantly (P<0.05) higher renal adrenergic responsiveness as compared with their non-renal failure controls. The data showed that in the renal failure WKY and SHR rats, the altered renal hemodynamics might be caused by an augmented renal adrenergic responsiveness. The results obtained further led us to suggest that the augmented renal adrenergic responsiveness in the cisplatin-induced renal failure rats were possibly mediated by the alpha(1)-adrenoceptors.
Des-aspartate angiotensin I (DAA-I), an endogenous nonapeptide, counteracts several effects of angiotensin II on vascular tone. The aim of this study was to investigate the acute protective effect of DAA-I on endothelial function in the spontaneously hypertensive rat (SHR) as well as its effect on angiotensin II-induced contractions and oxidative stress. Aortic rings were incubated with DAA-I (0.1μM) for 30min prior to the assessment of angiotensin II-induced contractions (0.1nM-10μM) in WKY and SHR aortas. Total nitrate and nitrite levels were assessed using a colorimetric method and reactive oxygen species (ROS) were measured by dihydroethidium (DHE) fluorescence and lucigenin-enhanced chemiluminescence. The effect of DAA-I was also assessed against endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside, respectively. Angiotensin II-induced contractions were significantly reduced by DAA-I, losartan and tempol. Incubation with ODQ (soluble guanylyl cyclase inhibitor) and removal of the endothelium prevented the reduction of angiotensin II-induced contractions by DAA-I. Total nitrate and nitrite levels were increased in DAA-I, losartan and tempol treated-SHR tissues while ROS level was reduced by DAA-I and the latter inhibitors. In addition, DAA-I significantly improved the impaired acetylcholine-induced relaxation in SHR aortas whilst sodium nitroprusside-induced endothelium-independent relaxation remained unaffected. The present findings indicate that improvement of endothelial function by DAA-I in the SHR aorta is mediated through endothelium-dependent release of nitric oxide and inhibition of angiotensin II-induced oxidative stress.
Precise uterine fluid pH regulation may involve the Na(+)/H(+)-exchanger (NHE). We hypothesized that NHE isoforms are differentially expressed under different sex steroid treatment and at different oestrous cycle phases which may explain the uterine fluid pH changes observed under these conditions.
Oxidative stress is implicated in the pathogenesis and/or complications of hypertension and/or diabetes mellitus. A combination of these disorders increases the risk of developing cardiovascular events. This study investigated the effects of streptozotocin (60 mg/kg; ip)-induced diabetes on blood pressure, oxidative stress and effects of honey on these parameters in the kidneys of streptozotocin-induced diabetic Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Diabetic WKY and SHR were randomized into four groups and received distilled water (0.5 mL) and honey (1.0 g/kg) orally once daily for three weeks. Control SHR had reduced malondialdehyde (MDA) and increased systolic blood pressure (SBP), catalase (CAT) activity, and total antioxidant status (TAS). SBP, activities of glutathione peroxidase (GPx) and glutathione reductase (GR) were elevated while TAS was reduced in diabetic WKY. In contrast, SBP, TAS, activities of GPx and GR were reduced in diabetic SHR. Antioxidant (honey) treatment further reduced SBP in diabetic SHR but not in diabetic WKY. It also increased TAS, GSH, reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio, activities of GPx and GR in diabetic SHR. These data suggest that differences in types, severity, and complications of diseases as well as strains may influence responses to blood pressure and oxidative stress.
1. There is a growing interest in the anti-oxidant characteristics and use of flavonoids in the management of cardiovascular diseases. The cardiovascular mechanism of action of these plant derivatives remains controversial. This study compared the effects of the flavonoid quercetin with those of the anti-oxidant vitamin ascorbic acid (vitamin C) on the reactivity of aortic rings from spontaneously hypertensive rats (SHR). 2. The phenylephrine (PE)-induced contractile and the endothelium-dependent and independent relaxant responses of aortic rings from 21 to 22 week old SHR and age-matched normotensive Wistar (WKY) rats were observed in the presence of quercetin or ascorbic acid. All the experiments were performed in the presence of the cyclooxygenase inhibitor, indomethacin (10 micromol/L). 3. The endothelium-dependent and independent relaxations to acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were significantly lesser in the SHR compared to the WKY tissues whereas the contractile responses to PE were similar in both tissues. Pretreatment of WKY rings with quercetin or ascorbic acid had no effect on the responses to ACh or PE. In the SHR tissues, however, quercetin or ascorbic acid significantly improved the relaxation responses to ACh and reduced the contractions to PE with greater potency for quercetin. Both compounds lacked any effects on the responses to SNP in either aortic ring types. N(omega)-nitro-L-arginine methyl ester (l-NAME, 10 micromol/L) significantly attenuated the vasodepressor effects of quercetin and ascorbic acid, raising the responses to PE to a level similar to that observed in the control SHR tissues. In l-NAME pretreated aortic rings, quercetin and ascorbic acid inhibited the contractile responses to PE with the same magnitude in WKY and SHR tissues. 4. The present results suggest that acute exposure to quercetin improves endothelium-dependent relaxation and reduces the contractile responses of hypertensive aortae with a greater potency than ascorbic acid. This suggests a better vascular protection with this flavonoid than ascorbic acid in the SHR model of hypertension and possibly in human cardiovascular diseases.
The aim of the present study was to investigate the effectiveness of transforming growth factor (TGF)-beta1 antisense oligodeoxynucleotides (ODN) in ameliorating deteriorated kidney function in rats with puromycin-induced chronic renal failure (CRF).
The effect of acidosis on insulin-induced relaxation was studied in thoracic aortic rings (from Wistar-Kyoto (WKY) rats) with (+ED) or without (-ED) endothelium. The rings were mounted in normal (pH 7.4) or acidotic (pH 7.2) Krebs solution for isometric tension recording. Phenylephrine (PE, 3.0 microM)-contracted tissues were exposed to insulin in the presence or absence of various inhibitors. Insulin exerted similar concentration-dependent relaxation of +ED tissues in normal and acidotic pH. Endothelium denudation, significantly (p<0.05) reduced insulin effect in normal, but not acidotic pH. Under normal pH, treatment with L-NAME or methylene blue significantly (p<0.05) reduced insulin responses in the +ED (but not the -ED) tissues. The insulin effect was also significantly (p<0.05) inhibited by tetraethylammonium (TEA; BK(Ca) blocker), 4-Aminopyridine (4-AP; K(V) channel blocker), combined treatments (L-NAME+4-AP+TEA, in +ED tissues) or (4-AP+TEA, in -ED tissues). In either +ED or -ED tissues, indomethacin (cyclo-oxygenase inhibitor), glibenclamide (K(ATP) channel blocker), barium chloride (K(ir) channel blocker) or Ouabain (a Na(+)/K(+)-ATPase inhibitor) had no effect. Except for methylene blue (effect on +ED tissues), none of the drug treatments inhibited insulin vasodilator effect in acidosis (+ED or -ED tissues). These data indicate that insulin exerts an endothelium-dependent and -independent vasodilatation in rat aorta which in normal pH is mediated via BK(Ca) and K(v) channels, including the EDNO-cGMP cascade. Acidosis abolishes the endothelium-dependent relaxation mechanism unraveling a novel mechanism that is as efficacious and is cGMP-, but not EDNO-, BK(Ca)- or K(v)-mediated.
The aim of this study was to determine the effects of alpha-tocopherol on lipid peroxidation and total antioxidant status of spontaneously hypertensive rats (SHR), comparing them with normal Wistar-Kyoto (WKY) rats. SHR were divided into three groups and treated with different doses of alpha-tocopherol (alpha1, 17 mg/kg diet; alpha2, 34 mg/kg diet; and alpha3, 170 mg/kg diet). Normal WKY and untreated SHR were used as normal (N) and hypertensive control (HC). Blood pressures were recorded every 10 days for 3 months. At the end of the trial, animals were killed and measurement of plasma total antioxidant status, plasma superoxide dismutase (SOD) activity, and lipid peroxide levels in plasma and blood vessels was carried out following well-established methods. From our study it was found that lipid peroxides in thoracic aorta (N, 0.47 +/- 0.17; H, 0.96 +/- 0.37; P < .0001) and plasma (N, 0.06 +/- 0.01; H, 0.13 +/- 0.01) were significantly higher in hypertensives than in normal rats. SOD activity was significantly lower in hypertensive than normal rats (N, 172.93 +/- 46.91; H, 110.08 +/- 14.38; P < .005). Total antioxidant status was significantly higher in normal than hypertensive rats (N, 0.88 +/- 0.05; H, 0.83 +/- 0.02; P < .05). After the antioxidant trial, it was found that in the treated groups rise of blood pressure was prevented significantly (P < .001) and lipid peroxides in blood vessels were significantly reduced more than in the controls (P < .001). For plasma lipid peroxide it was only significant for groups alpha2 (P < .001) and alpha3 (P < .05). Although all three treated groups showed improved total antioxidant status, only groups alpha2 (0.87 +/- 0.04, P < .005) and alpha3 (1.20 +/- 0.18, P < .001) were statistically significant. All the three groups showed significant increases in their SOD activity (P < .001). Correlation studies showed that total antioxidant status and SOD were significantly negatively correlated with blood pressure in normal rats (P = .007; P = .008). Lipid peroxides in both blood vessel and plasma showed a positive correlation. In the treated groups, lipid peroxides in blood vessels maintained a significant positive correlation with blood pressure in all groups (alpha1, P = .021; alpha2, P = .019; alpha3, P = .002), whereas for plasma lipid peroxides the correlation was in groups alpha1 (P = .005) and alpha2 (P = .009). For SOD activity, significant negative correlations were found with blood pressure in the alpha2 (P = .017) and alpha3 (P = .025) groups. Total antioxidant status maintained a significant negative correlation with blood pressure in all three groups (alpha1, P = .012; alpha2, P = .044; alpha3, P = .014). In conclusion it was found that supplement of alpha-tocopherol may prevent development of increased blood pressure, reduce lipid peroxides in plasma and blood vessels, and enhance the total antioxidant status, including SOD activity.
An antisense oligodeoxynucleotide (As-ODN) to the 3' untranslated region of the mRNA sequence expressing the intracellular adhesion molecule-1 (ICAM-1) was employed to determine ICAM-1's role in renal ischaemia-reperfusion injury in the rat. Wistar-Kyoto rats receiving i.v. either lipofectin-As-ODN (As-ODN group), lipofectin-reverse ODN (Rv-ODN group) or lipofectin (ischaemia control group) 8 h prior to study were anaesthetized and subjected to 30 min of renal artery occlusion. Renal haemodynamic and excretory parameters were monitored before and after renal ischaemia. On termination of the study renal tissue was subjected to histological and Western blot analysis. Renal blood flow decreased in the 3 h post-ischaemia period in the ischaemia control and Rv-ODN groups, but was maintained in the As-ODN group. Glomerular filtration rate was depressed initially but gradually increased to 10% above basal levels in the ischaemia control and Rv-ODN groups, but was below basal levels (20%) in the As-ODN group. There was a three- to fourfold increase in sodium and water excretion following ischaemia in the ischaemia control and reverse-ODN groups but not in the As-ODN treated group. The As-ODN ameliorated the histological evidence of ischaemic damage and reduced ICAM-1 protein levels to a greater extent in the medulla than cortex. These observations suggested that in the post-ischaemic period afferent and efferent arteriolar tone was increased with a loss of reabsorptive capacity which was in part due to ICAM-1. The possibility arises that the action of ICAM-1 at vascular and tubular sites in the deeper regions of the kidney contributes to the ischaemia-reperfusion injury.
The present study was conducted to examine the effect of bradykinin and bradykinin 2 receptor antagonist on survival time in rats with coronary artery ligation for 15 min and continuously. We also evaluated the heart rate and blood pressure responses in the presence and absence of bradykinin and its antagonist. Bradykinin treatment (4 microg and 8 microg/kg IV) significantly (p < 0.05) increased the survival time of rats compared with saline-treated rats with coronary artery ligation for 15 min and continuously. The heart rate and blood pressure responses were significantly (p < 0.001) altered in the presence of coronary artery ligation. Bradykinin antagonist treatment (4 microg/kg IV) abolished the effect of bradykinin and thus reduced the survival time of rats with coronary artery ligation. The mean value of survival time between saline-treated and bradykinin antagonist- plus bradykinin-treated rats did not differ significantly (p > 0.05).