Production of lysophosphatidic acid by lysophospholipase D in incubated plasma of spontaneously hypertensive rats and Wistar Kyoto rats.

Lysophosphatidic acid has been identified as a vasopressor principle in incubated mammalian plasma and sera, and shown to be generated extracellulary by lysophospholipase D-like activity. In this study, we monitored the time course of changes in the major phospholipid fractions during incubation of plasma, and found that polyunsaturated lysophosphatidic acids accumulate more rapidly than saturated lysophosphatidic acids at expense of the corresponding lysophosphatidylcholines. We compared the phospholipase activities for producing bioactive LPA in age-matched spontaneously hypertensive rats and Wistar Kyoto rats. The lysophospholipase D activity in rat plasma was found to be independent of strain and age. We suggest that lysophospholipase D functions in rat for persistent production of bioactive LPA in the circulation throughout life. However, our finding that production of LPA in spontaneously hypertensive rats was not greater than that in Wistar Kyoto rats does not seem to support the idea that increased production of LPA is involved in the pathogenesis of hypertension.     

Sensitivity of spontaneously hypertensive and of Wistar Kyoto rats to the antidipsogenic action of eledoisin

This study investigated the sensitivity of spontaneously hypertensive rats (SHR) and of Wistar Kyoto rats (WKR) to the antidipsogenic action of the tachykinin eledoisin (ELE). Drinking was evoked by: (a) intracerebroventricular (i.c.v.) injection of angiotensin II, (b) subcutaneous (s.c.) administration of hypertonic NaCl (1.5 M; 1 ml/100 g b.wt.) or (c) 18 h of water deprivation with free access to food. In accordance with previous studies, the dipsogenic effect of all three treatments was exaggerated in the SHR. And when treated with i.c.v. ELE (12.5-25 ng/rat) they were far less sensitive than WKR to its antidipsogenic action on angiotensin-induced drinking. Smaller differences in strain sensitivity were also observed for the effect of ELE on cell dehydration- and on water deprivation-induced drinking, but only at the dose of 200 and 50 ng/rat, respectively. The different sensitivity of the SHR to the antidipsogenic effect of ELE supports the idea that tachykininergic mechanisms for control of water intake are differently regulated in the SHR than they are in the normotensive WKR.     

Adrenal hydroxylations in genetically obese and hypertensive rats.

The separate steps in the formation of aldosterone from cholesterol were studied in a strain of spontaneously hypertensive rats in which phenotypic obesity is inherited as a recessive trait (Koletsky rats). The obese and hypertensive state had little or no effect on side-chain cleavage of cholesterol, formation of progesterone from pregnenolone or 21-hydroxylation. Mitochondrial 18-hydroxylation of endogenous and exogenous corticosterone, however, as well as 18- and 11 beta-hydroxylation of deoxycorticosterone, were increased in obese hypertensive rats, both when compared with non-obese hypertensive siblings and when compared with healthy Sprague-Dawley rats. 18-Hydroxylation of corticosterone was increased more than 18-hydroxylation of deoxycorticosterone. In non-obese hypertensive rats, the adrenal content of mitochondrial cytochrome P-450 was lower than that in obese hypertensive rats but higher than that in rats of the conventional Sprague-Dawley strain. The results are discussed with respect to possible heterogeneity of adrenal cytochrome P-450 and to possible explanations for the changes observed.     

Protein kinase C activity in platelets from spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY)

Calcium-activated phospholipid dependent protein kinase (protein kinase C) activity in platelets was measured in 4, 12, and 20-week-old SHR and WKY. At age 4-weeks, there was no significant difference in protein kinase C activity and systolic blood pressure between SHR and WKY. In 12 and 20-week-old SHR, both protein kinase C activity and systolic blood pressure were significantly higher than in the age-matched WKY. These results suggest that protein kinase C may be involved in the control of blood pressure in SHR and WKY.     

Gene Expression Profiling of Cultured Cells From Brainstem of Newborn Spontaneously Hypertensive and Wistar Kyoto Rats

The spontaneously hypertensive rat (SHR) is a good model to study several diseases such as the attention-deficit hyperactivity disorder, cardiopulmonary impairment, nephropathy, as well as hypertension, which is a multifactor disease that possibly involves alterations in gene expression in hypertensive relative to normotensive subjects. In this study, we used high-density oligoarrays to compare gene expression profiles in cultured neurons and glia from brainstem of newborn normotensive Wistar Kyoto (WKY) and SHR rats. We found 376 genes differentially expressed between SHR and WKY brainstem cells that preferentially map to 17 metabolic/signaling pathways. Some of the pathways and regulated genes identified herein are obviously related to cardiovascular regulation; in addition there are several genes differentially expressed in SHR not yet associated to hypertension, which may be attributed to other differences between SHR and WKY strains. This constitute a rich resource for the identification and characterization of novel genes associated to phenotypic differences observed in SHR relative to WKY, including hypertension. In conclusion, this study describes for the first time the gene profiling pattern of brainstem cells from SHR and WKY rats, which opens up new possibilities and strategies of investigation and possible therapeutics to hypertension, as well as for the understanding of the brain contribution to phenotypic differences between SHR and WKY rats.     

Effects of nitric oxide synthase inhibitor on tyrosine hydroxylase mRNA in the adrenal medulla of spontaneously hypertensive and Wistar Kyoto rats.

We studied the effects of N(G)-nitro-l-arginine methyl ester (L-NAME) on catecholamine levels, tyrosine hydroxylase (TH) activity, and TH mRNA levels in the adrenal medulla of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). L-NAME (100 mg/L in drinking water) and atropine (10 mg/L in drinking water) were administered for 2 weeks. Epinephrine and norepinephrine levels, TH activity, and TH mRNA levels in the adrenal medulla of L-NAME-treated WKY were significantly decreased. These parameters were not significantly altered in the adrenal medulla of L-NAME-treated SHR. Nitrite/nitrate levels in the adrenal medulla of L-NAME-treated WKY were significantly decreased; however, no significant change in L-NAME-treated SHR was observed. Ca(2+)-dependent nitric oxide synthase (NOS) activity in the adrenal medulla of SHR was significantly decreased compared to that of WKY. TH mRNA levels in L-NAME + atropine-treated and L-NAME-treated WKY were significantly lower than TH mRNA levels in control WKY. These results suggest that nitric oxide in the adrenal medulla may enhance the catecholamine biosynthetic pathway via increased TH mRNA expression. Our results also suggest that this effect is suppressed in SHR due to decreased NOS activity in the adrenal medulla.     

Plasma renin activity and electrolyte and water metabolism in normal and in genetically hypertensive (Okamoto) Wistar rats

The electrolyte and water metabolisms and plasma renin activity (PRA) were investigated in genetically hypertensive (Okamoto) and in normotensive Wistar rats. The water intake, PRA, urine volume, urinary Na excretion and Na/K ratio were all found to be smaller in the genetically hypertensive rats than in the controls. No relationship could be demonstrated between PRA values and water intake.     

Dysfunction of supramedullary alpha-adrenergic mechanisms following sino-aortic denervation in Kyoto Wistar rats

Central α-adrenergic mechanisms of blood pressure regulation were investigated by injecting norepinephrine or bradykinin into the carotid input of the cross-circulated head preparations of normotensive Wistar Kyoto rats (WKY). Rats were divided into three groups: sham-operated (sham), carotid sinuses denervated (SD) and carotid sinuses and aortic nerves debuffered (SAD). Norepinephrine, 5 μg, produced vasodepression in all rats, accompanied by corresponding decreases in sympathetic nerve activity recorded in some rats. Magnitude of vasodepression was largest in SAD rats. In sham rats, bradykinin, 1 μg, produced a biphasic response:initial vasodepression followed by a sustained pressor phase. This was accompanied by corresponding changes in peripheral sympathetic nerve activity recorded in some rats. In both SAD and SD rats bradykinin-induced vasodepression was abolished, while the magnitude of the pressor phase became more prominent. The increase in the pressor phase was greater in SAD than in SD rats. In similar studies of spontaneously hypertensive rats (SHR), responses to both α-adrenergic agonist and bradykinin are augmented, suggesting a dysfunction of hypothalamic α-adrenergic mechanisms. Since in the present study it has been shown that sino-aortic denervation produces effects similar to those seen in SHR, dysfunction of buffer nerves may account for the deficient central α-adrenergic mechanisms in SHR.     

Spontaneously hypertensive rats exhibit supersensitivity to the hypertensive and hyperthermic effects of thyrotropin releasing hormone

The effect of thyrotropin releasing hormone (TRH) on colonic temperature and systolic blood pressure of age-matched spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats was determined. Administration of TRH produced dose-dependent increases in body temperature and systolic blood pressure. TRH-induced changes in both responses were of greater magnitude in SHR rats compared to WKY rats. The results provide the first evidence that SHR rats exhibit supersensitivity to non-neuroendocrinological effects of TRH and that TRH may play a role in the pathophysiology of elevated blood pressure.     

Kidney adaptation in nitric oxide-deficient Wistar and spontaneously hypertensive rats

We investigated the renal structural and functional consequences of nitric oxide (NO) deficiency co-treated with angiotensin-converting enzyme inhibitor (ACEi) in 20 adult male Wistar rats and 20 spontaneously hypertensive rats (SHR). The animals were separated into eight groups (n = 5) and treated for 30 days: Control, L-NAME (NO deficient group), Enalapril, L-NAME + Enalapril. The elevated blood pressure in NO deficient rats was partially reduced by enalapril. Serum creatinine was elevated in L-NAME-SHRs and effectively treated with enalapril. The proteinuria was significantly higher only in L-NAME-SHRs, and this was reduced by treatment with ACEi. The glomerular volume density (Vv(gl)) in L-NAME rats, both Wistar and SHR, was greater than in matched control rats, and enalapril treatment effectively prevented this Vv(gl) increase. No significant differences were observed in tubular volume density, Vv(tub), or tubular surface density, Sv(tub), in all Wistar groups. The Vv(tub) was smaller in L-NAME-SHRs than in control SHRs, and this tubular alteration was not prevented by enalapril. The Sv(tub) was not different among the SHR groups. In Wistar rats no changes were seen in vascular surface density, but a greatly increased cortical vascular volume density was seen in the enalapril treated rats. The vascular length density was greatly diminished in NO deficient rats that was effectively prevented with enalapril treatment. The vascular cortical renal stereological indices are normally reduced in SHRs. Administration of enalapril, but not L-NAME, changed this tendency. However, enalapril was not totally effective in preventing vascular damage in SHR NO deficient animals.     

Hepatic biotransformation in lean and obese Wistar Kyoto rats: comparison to that in streptozotocin-pretreated Sprague-Dawley rats

1. Phase I and phase II biotransformation was compared in streptozotocin-induced hypoinsulinemic (STZ) and genetic hyperinsulinemic (WKY-fatty) rats. 2. Total cytochrome P-450 concentrations were reduced in both STZ and WKY, whereas styrene oxide hydrolase and benzphetamine N-demethylase activities were normal in STZ and reduced in WKY. 3. UDP-glucuronosyltransferase activity was decreased toward testosterone and 1-naphthol in STZ and WKY, and was increased toward estrone in the obese female WKY. 4. Glutathione S-transferase activity was decreased in STZ toward 1-chloro-2,4-dinitrobenzene, ethacrynic acid and sulfobromophthalein, but was similar to that in normal rats for WKY.     

Brain insulin binding is decreased in Wistar Kyoto rats carrying the 'fa' gene

We have previously reported that insulin binding is decreased in the olfactory bulb of both heterozygous (Fa/fa) and obese (fa/fa) Zucker rats. In the present study, we measured insulin binding in membranes prepared from the olfactory bulb, cerebral cortex, and hypothalamus of control (Fa/Fa) Wistar Kyoto rats; "fatty" (fa/fa) Wistar Kyoto rats; and phenotypically lean (Fa/?) Wistar Kyoto rats. Insulin binding was decreased in all brain regions, as well as the liver of the obese Wistar Kyoto fa/fa rats. Additionally, insulin binding was decreased in the liver and brain membranes from the Fa/? Wistar Kyoto rats. As most of the Fa/? rats were probably carriers of one 'fa' gene, but the population was only slightly hyperinsulinemic, we conclude that--as in the Zucker rat--it is the presence and expression of the 'fa' gene rather than downregulation which results in the decreased insulin binding. Thus, regulation of the brain insulin receptor appears to be independent of plasma or cerebrospinal fluid insulin levels.     

Inhalation of Roman chamomile essential oil attenuates depressive-like behaviors in Wistar Kyoto rats

The idea of aromatherapy, using essential oils, has been considered as an alternative antidepressant treatment. In the present study, we investigated the effect of Roman chamomile essential oil inhalation for two weeks on depressive-like behaviors in Wistar-Kyoto(WKY) rats. We found that inhalation of either Roman chamomile or one of its main components α-pinene,attenuated depressive-like behavior in WKY rats in the forced swim test. Using isobaric tags for relative and absolute quantitation analysis(iTRAQ), we found that inhalation of α-pinene increased expression of proteins that are involved in oxidative phosphorylation, such as cytochrome c oxidase subunit 6C-2, cytochrome c oxidase subunit 7A2, ATPase inhibitor in the hippocampus, and cytochrome c oxidase subunit 6C-2, ATP synthase subunit e, Acyl carrier protein, and Cytochrome b-c1 complex subunit 6 in the PFC(prefrontal cortex). In addition, using the quantitative real-time polymerase chain reaction technique, we confirmed an increase of parvalbumin mRNA expression in the hippocampus, which was shown to be upregulated by 2.8-fold in iTRAQ analysis, in α-pinene treated WKY rats. These findings collectively suggest the involvement of mitochondrial functions and parvalbumin-related signaling in the antidepressant effect of α-pinene inhalation.     

Protein kinase C activity and reactivity to phorbol ester in vascular smooth muscle from spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY)

Protein kinase C (PKC) activity in aortic and renal arterial smooth muscle from SHR (20-23 wk male; mean arterial pressure = 178 mm Hg) and WKY (age/sex matched; mean arterial pressure = 126 mm Hg) was quantitated. Activity was greatest in the particulate fractions relative to the soluble fractions in all sources. The only difference between SHR and WKY was in the soluble fraction from SHR renal arteries, which had 2 fold more activity (255 pmol/mg/min) when compared with WKY (136 pmol/mg/min). This difference was not apparently related to force modulation, since the magnitude of isometric force development in renal arteries in response to phorbol 12,13-dibutyrate was not different between SHR and WKY. The magnitude of force developed in response to phorbol 12,13-dibutyrate and PKC activity in the particulate fraction was greatest in aorta vs. renal arteries in both WKY and SHR. These results suggest that regional vascular differences in the amount of PKC activity may exist which are not apparently related to a disease state (i.e., hypertension). These differences may be related to differential sensitivity to phorbol ester-mediated contractions in isolated smooth muscle.     

Effects of endothelin 3 on diastolic blood pressure of pithed Sprague-Dawley, Wistar Kyoto, and spontaneously hypertensive rats before and after pretreatment with nifedipine

Pressor actions of endothelin 3 (ET3) were examined in pithed Sprague-Dawley (SD), Wistar-Kyoto (WKY), and spontaneously hypertensive (SH) rats before and after the administration of the calcium channel antagonist, nifedipine. Systolic and diastolic blood pressures were recorded via an intra-arterial catheter from sodium pentobarbital anaesthized rats prior to pithing. The systolic and diastolic blood pressures recorded from SH rats were significantly greater than those of SD and WKY rats; however, after pithing there were no significant differences between the diastolic blood pressures among the various strains. Administration of nifedipine significantly reduced the diastolic blood pressure of pithed rats to an equal extent in all three strains. The infusion of ET3 produced a dose-dependent increase in diastolic blood pressure of SD, WKY, and SH rats, but neither vascular sensitivity nor reactivity to ET3 was altered in SH rats. Nifedipine was more effective at inhibiting the vasoactive actions of ET3 in SD and WKY than in SH rats. It was therefore concluded that the pressor actions of ET3 in SH rats may be less dependent on the influx of calcium through a dihydropyridine-sensitive calcium channel as compared with WKY and SD rats.     

Hypothesis with abnormal amino acid metabolism in depression and stress vulnerability in Wistar Kyoto rats

While abnormalities in monoamine metabolism have been investigated heavily per potential roles in the mechanisms of depression, the contribution of amino acid metabolism in the brain remains not well understood. In additional, roles of the hypothalamus–pituitary–adrenal axis in stress-regulation mechanisms have been of much focus, while the contribution of central amino acid metabolism to these mechanisms has not been well appreciated. Therefore, whether depression-like states affect amino acid metabolism and their potential roles on stress-regulatory mechanisms were investigated by comparing Wistar Kyoto rats, which display depression-like behaviors and stress vulnerability, to control Wistar rats. Brain amino acid metabolism in Wistar Kyoto rats was greatly different from normal Wistar rats, with special reference to lower cystathionine and serine levels. In addition, Wistar Kyoto rats demonstrated abnormality in dopamine metabolism compared with Wistar rats. In the case of stress response, amino acid levels having a sedative and/or hypnotic effect were constant in the brain of Wistar Kyoto rats, though these amino acid levels were reduced in Wistar rats under a stressful condition. These results suggest that the abnormal amino acid metabolism may induce depression-like behaviors and stress vulnerability in Wistar Kyoto rats. Therefore, we hypothesized that abnormalities in amino acid and monoamine metabolism may induce depression, and amino acid metabolism in the brain may be related to stress vulnerability.