WKY Animals Research Articles

Изменения клеток Колмера у крыс линии SHR после ишемии головного мозга

Kolmer cells (epiplexus macrophages) are the least studied population of phagocytic cells in the mammalian brain. In the present work, we studied the response of these cells to high blood pressure and ischemic brain injury caused by a short middle cerebral artery occlusion. We used spontaneously hypertensive SHR and normotensive WKY rats. Kolmer cells of normotensive WKY animals had a small volume of perinuclear cytoplasm with a cortical concentration of Iba-1 protein. These cells had characteristic thin, sometimes tortuous processes. Moderate activation due to high blood pressure in SHR rats was accompanied by an increase in the perinuclear cytoplasm volume and the appearance of numerous straight thin processes. Further activation caused by ischemia led to the disappearance of processes and the cells became round. The structural rearrangements were accompanied by the disappearance of the Iba-1 protein concentration gradient in the cytoplasm. Also, the intranuclear accumulation of the cytoplasmic Iba-1 protein in Kolmer cells was first discovered, independent of their activation. That indicates the polyfunctionality of this protein in the cell. The obtained results point to the involvement of Kolmer cells in the brain's response to injury.

Increased oxytocinergic system activity in the cardiac muscle in spontaneously hypertensive SHR rats.

IntroductionThe present study aimed to determine whether the presence of cardiac hypertrophy due to arterial hypertension is associated with a change in the activity of the oxytocinergic system in cardiomyocytes.Material and methodsThe experiments were performed on male, spontaneously hypertensive rats (SHR, n = 10) and normotensive Wistar-Kyoto rats (WKY, n = 12). Blood samples were collected from both SHR and WKY animals to asses plasma oxytocin (OT) concentration; the rats were sacrificed by decapitation. Samples of the left and right ventricles were harvested for the analysis of the OT and oxytocin receptor (OTR) protein by ELISA, and OT and OTR mRNA expression by RT-PCR. Immunohistopathological studies were performed to confirm the presence of OTR receptors in the cardiac muscle of the ventricles.ResultsPlasma OT concentration did not differ between SHR and WKY rats. In the SHR rats, the expression of OT mRNA and the OT protein level was higher in the left and the right ventricle, while OTR mRNA expression was significantly lower in both the left and the right ventricle. However, the level of OTR protein was higher only in the left ventricle of the SHR rats. The presence of OTR receptors was confirmed by immunohistochemical analysis in the muscle of the right and left ventricle.ConclusionsThe presence of arterial hypertension is associated with increased activity of the oxytocinergic system in the heart, especially in the area of the left ventricle. These findings support the important role of this system in the maintenance of cardiovascular homeostasis.

Abstract WP427: Examining the Role of Gut Dysbiosis in Cerebral Small Vessel Disease

The importance of a healthy gut microbiota on host physiology is becoming increasingly evident. Recent studies suggest that alterations to the microbiota can have adverse effects beyond the GI tract, and has been linked to hypertension and stroke. Thus we hypothesized that gut dysbiosis could contribute to the development of cerebral small vessel disease (CSVD). Giving merit to this hypothesis, we found that the microbiota of the spontaneously hypertensive stroke prone rat (SHRSP) is significantly different than that of WKY controls. Using 16s rRNA sequencing of bacterial DNA we found that SHRSP animals had decreases in measures of bacterial richness (p=.005) and diversity (p=.028), indicative of gut dysbiosis. Phenotypically, CSVD includes vessel remodeling, BBB breakdown and neuroinflammation. Gut dysbiosis is often associated with a leaky gut barrier that allows bacteria to enter the systemic circulation. We observed significantly greater permeability of the SHRSP colon barrier when compared to WKY (p=.026). We next sought to determine if impaired colon barrier function in SHRSP could lead to increased bacterial translocation to the periphery and ultimately to the brain. Brains were harvested from 24 week old SHRSP and WKY animals and qRT-PCR of the 16s rRNA gene was performed to detect the presence of bacteria in the brain. We discovered that SHRSP animals displayed a 50% increase in bacterial 16S rRNA load in the brain compared to WKY animals (p=.0063) confirming that bacteria are not only present in CSVD rats, but also in greater abundance than WKYs. Similarly, we found that SHRSP animals displayed a near 2-fold increase of the bacterial endotoxin LPS in the brain, as compared to WKY brain LPS levels (p=.01). Finally, to further confirm the presence of bacterial components in the brain we used immunofluorescence imaging to visualize peptidoglycan (PG), a molecule found solely in bacterial cell walls. We discovered that we could visualize the presence of PG in the brains of SHRSP animals, and note that PG was commonly observed inside microglia. We conclude from this study that SHRSP rats exhibit gut dysbiosis, gut barrier breakdown, and bacterial products in the brain. Further studies will examine how this bacterial presence contributes to the CSVD phenotypes.

Neuropathy in the spontaneously hypertensive rat: An electrophysiological and histological study.

Hypertension is identified as a risk factor for development of polyneuropathy. In this study we examined nerve conduction and morphological alteration of peripheral nerves in spontaneously hypertensive rats (SHR). Motor nerve conduction velocity (MNCV) in the sciatic-tibial nerve and sensory nerve conduction velocity (SNCV) in the sural nerve were measured. Pathological investigations included spinal cord, dorsal root ganglion, and hindlimb nerves in SHR and Wistar-Kyoto rats (WKY) aged 4-64 weeks. Blood pressure was significantly higher in SHR than WKY animals at 4 weeks and elevated further with aging. MNCV and SNCV were significantly slower in SHR compared with WKY after age 24 weeks. Prominent morphological changes in SHR nerves included axonal atrophy and myelin splitting. SHR also had endoneurial microangiopathy with reduplication of basement membrane. SHR showed slowed nerve conduction velocity and pathological abnormalities of hindlimb nerves. Sustained severe hypertension may cause axonal atrophy and endoneurial microangiopathy. Muscle Nerve 54: 756-762, 2016.

Evidences of antihypertensive potential of extract from Solanum capsicoides All. in spontaneously hypertensive rats

BackgroundSolanum capsicoides All. is morphologically similar to Solanum sisymbriifolium Lam. which is used in folk medicine in South America for antihypertensive and diuretics purposes. This similarity has led to species identification errors, which therefore may result in errors by patients. PurposeTo evaluate the antihypertensive and diuretics potential of the methanol extract from Solanum capsicoides All. (MeOH–Sc), in vitro and in vivo, in spontaneously hypertensive rats (SHR). MethodsInitial experiments were performed in rat mesenteric artery to evaluate the in vitro vascular effect of MeOH–Sc and its fractions, in addition to the mechanisms involved during the observed effect. Mean arterial pressure (MAP) and heart rate (HR) were recorded in non-anesthetised hypertensive and normotensive rats. In another set of experiments, MeOH–Sc was administered for 21 consecutive days. Daily body weight measurements were conducted and MAP, HR and urinary volume were measured every 5 days. The mesenteric artery from treated animals was tested for phenylephrine and sodium nitroprussiate (SNP) sensitivity. ResultsInitially, MeOH–Sc and fractions relaxed phenylephrine-induced contractions in mesenteric artery rings. The vasorelaxant effect was not changed in the presence of a blocker of eNOS (L-NAME) in rings with an intact endothelium. In denuded-endothelium rings, the vasorelaxant response was significantly reduced in the presence of a cAMP inhibitor (SQ 22536 10µM) in SHR but not in Wistar Kyoto rats (WKY). However, in the presence of a cGMP inhibitor (ODQ 10µM), a curve shift to the right was observed in WKY animals, but not in SHR. Intravenous bolus injections of MeOH–Sc into non-anesthetised SHR and WKY, induced hypotension that was associated with an increase in HR. A significant antihypertensive effect was observed in animals that received MeOH–Sc orally for 21 days, which also prevented the development of cardiac hypertrophy. Urine volume from animals treated with MeOH–Sc significantly increased. Finally, MeOH–Sc induced beneficial changes in vascular responsiveness. ConclusionMeOH–Sc has a potential antihypertensive effect in SHR.

The Effects of Methylphenidate on Goal-directed Behavior in a Rat Model of ADHD.

Although attentional and motor alterations in Attention Deficit Hyperactivity Disorder (ADHD) have been well characterized, less is known about how this disorder impacts goal-directed behavior. To investigate whether there is a misbalance between goal-directed and habitual behaviors in an animal model of ADHD, we tested adult [P75–P105] Spontaneously Hypertensive Rats (SHR; ADHD rat model) and Wistar–Kyoto rats (WKY), the normotensive control strain, on an instrumental conditioning paradigm with two phases: a free-operant training phase in which rats separately acquired two distinct action–outcome contingencies, and a choice test conducted in extinction prior to which one of the food outcomes was devalued through specific satiety. To assess the effects of Methylphenidate (MPH), a commonly used ADHD medication, on goal-directed behavior, we injected rats with either MPH or saline prior to the choice test. Both rat strains acquired an instrumental response, with SHR responding at greater rates over the course of training. During the choice test WKY demonstrated goal-directed behavior, responding more frequently on the lever that delivered, during training, the still-valued outcome. In contrast, SHR showed no goal-directed behavior, responding equally on both levers. However, MPH administration prior to the choice test restored goal-directed behavior in SHR, and disrupted this behavior in WKY rats. This study provides the first experimental evidence for selective impairment in goal-directed behavior in rat models of ADHD, and how MPH acts differently on SHR and WKY animals to restore or impair this behavior, respectively.

Early-life stress selectively affects gastrointestinal but not behavioral responses in a genetic model of brain-gut axis dysfunction.

Early-life stress and a genetic predisposition to display an anxiety- and depressive-like phenotype are associated with behavioral and gastrointestinal (GI) dysfunction. Animals exposed to early-life stress, and those genetically predisposed to display anxiety or depressive behaviors, have proven useful tools in which to study stress-related GI disorders, such as irritable bowel syndrome (IBS). IBS is a heterogeneous disorder, and likely a consequence of both genetic and environmental factors. However, the combined effects of early-life stress and a genetic predisposition to display anxiety- and depression-like behaviors on GI function have not been investigated. We assessed the effect of maternal separation (MS) on behavioral and GI responses in WKY animals relative to a normo-anxious reference strain. Both non-separated (NS) WKY and WKY-MS animals displayed anxiety-like responses in the open-field test and depressive-like behaviors in the forced swim test relative to Sprague-Dawley rats. However, MS had no further influence on anxiety- and depressive-like behaviors exhibited by this stress-prone rat strain. Similarly, corticosterone levels measured after the OFT were insensitive to MS in WKY animals. However, WKY-MS displayed significantly increased colonic visceral hypersensitivity, fecal output, and altered colonic cholinergic sensitivity. Our data suggest that early-life stress, on the background of a genetic predisposition to display an anxiety- and depressive-like phenotype, selectively influences GI function rather than stress-related behaviors. Thus, our findings highlight the importance of genetic predisposition on the outcome of early-life adversity on GI function.

CARDIOTOXICITY OF CHRONIC SUNITINIB TREATMENT IN NORMOTENSIVE AND SPONTANEOUSLY HYPERTENSIVE RATS

AimsSunitinib is a modern multi-targeted tyrosine kinase inhibitor, which showed great promise in the treatment of human cancer. However, its chronic use may be associated with cardiotoxicity, which is poorly...

Hypotensive effect and endothelium-dependent vascular action of leaves of Alpinia purpurata (Vieill) K. Schum

The aims of this study were to evaluate the chemical profile, vascular reactivity, and acute hypotensive effect (AHE) of the ethanolic extract of leaves of Alpinia purpurata (Vieill) K. Schum (EEAP). Its chemical profile was evaluated using HPLC-UV, ICP-OES, and colorimetric quantification of total flavonoids and polyphenols. The vascular reactivity of the extract was determined using the mesenteric bed isolated from WKY. AHE dose-response curves were obtained for both EEAP and inorganic material isolated from AP (IAP) in WKY and SHR animals. Cytotoxic and mutagenic safety levels were determined by the micronucleus test. Rutin-like flavonoids were quantified in the EEAP (1.8 ± 0.03%), and the total flavonoid and polyphenol ratios were 4.1 ± 1.8% and 5.1 ± 0.3%, respectively. We observed that the vasodilation action of EEAP was partially mediated by nitric oxide (·NO). The IAP showed the presence of calcium (137.76 ± 4.08 μg mg-1). The EEAP and IAP showed an AHE in WKY and SHR animals. EEAP did not have cytotoxic effects or cause chromosomic alterations. The AHE shown by EEAP could result from its endothelium-dependent vascular action. Rutin-like flavonoids, among other polyphenols, could contribute to these biological activities, and the calcium present in EEAP could act in a synergistic way.

2042 DELETION AND MUTATION ANALYSIS OF RECOMBINATION GENES IN MEN WITH MEIOTIC DEFECTS

INTRODUCTION AND OBJECTIVES: The target organ damage is well documented in arterial hypertension, but testicular damage is not clearly defined. This study evaluates the testicular morphology and spermatozoid parameters of spontaneously hypertensive rats (SHR) treated or not with enalapril. METHODS: 28 adult SHR animals were assigned into two groups, a hypertensive group (H, n 13), and an enalapril treated group (HE, n 15). Wistar-Kyoto rats (WKY, n 8) were used as controls. Animals of group HE received 30mg/Kg of enalapril daily by gavage while H and WKY animals received tap water. Arterial systolic pressure was weekly measured by plethysmography. After five weeks of treatment, all animals were killed by anesthetic overdose. The right epididimal tail was removed and used for spermatozoid collection. Sperm concentration, motility and viability (hypo-osmotic test) were assessed. The right testicles were fixed and routinely processed for obtaining hematoxylin and eosin stained histological sections. In these sections, the seminiferous tubule diameter, epithelial height and relative densities of the testicular structures were assessed by stereological methods. All data was compared by ANOVA with Tukey’s post test, considering p 0.05 as significant. RESULTS: Blood pressure in the HE group were similar WKY, and lower than H animals. Spermatozoid concentration had a 38% reduction in hypertensive rats when compared to controls while enalapril treatment restored normal concentration. Concerning spermatozoid motility and viability, no difference was found among the groups. Testicular vascular volumetric density was also altered in hypertensive group while HE animals were similar to controls. The seminiferous epithelium of HE animals showed the highest volumetric density, indicating a positive effect of enalapril in spermatogenesis. The analysis of seminiferous tubule diameter and epithelium height showed no significant difference among the studied groups. Table 1 presents all numerical data. CONCLUSIONS: In the SHR model, hypertension induces testicular alterations both in seminiferous tubule and intratesticular vessels resulting in low spermatozoid concentration. Enalapril treatement partially protected the testicle from the hypertension-induced alterations, restoring normal spermatozoid production. Source of Funding: FAPERJ, CNPq and CAPES.

2041 TESTICULAR MORPHOLOGY AND SPERMATOZOID PARAMETERS IN HYPERTENSIVE RATS TREATED OR NOT WITH ENALAPRIL

You have accessJournal of UrologyInfertility: Basic Research, Physiology, Pathophysiology1 Apr 20132041 TESTICULAR MORPHOLOGY AND SPERMATOZOID PARAMETERS IN HYPERTENSIVE RATS TREATED OR NOT WITH ENALAPRIL Gustavo Bechara, Michele Simões, Bruno Felix-Patricio, Jorge Medeiros, Bianca Gregório, Diogo de Souza, Waldemar Costa, and Francisco Sampaio Gustavo BecharaGustavo Bechara Rio de Janeiro, Brazil More articles by this author , Michele SimõesMichele Simões Rio de Janeiro, Brazil More articles by this author , Bruno Felix-PatricioBruno Felix-Patricio Rio de Janeiro, Brazil More articles by this author , Jorge MedeirosJorge Medeiros Rio de Janeiro, Brazil More articles by this author , Bianca GregórioBianca Gregório Rio de Janeiro, Brazil More articles by this author , Diogo de SouzaDiogo de Souza Rio de Janeiro, Brazil More articles by this author , Waldemar CostaWaldemar Costa Rio de Janeiro, Brazil More articles by this author , and Francisco SampaioFrancisco Sampaio Rio de Janeiro, Brazil More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.2460AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The target organ damage is well documented in arterial hypertension, but testicular damage is not clearly defined. This study evaluates the testicular morphology and spermatozoid parameters of spontaneously hypertensive rats (SHR) treated or not with enalapril. METHODS 28 adult SHR animals were assigned into two groups, a hypertensive group (H, n=13), and an enalapril treated group (HE, n=15). Wistar-Kyoto rats (WKY, n=8) were used as controls. Animals of group HE received 30mg/Kg of enalapril daily by gavage while H and WKY animals received tap water. Arterial systolic pressure was weekly measured by plethysmography. After five weeks of treatment, all animals were killed by anesthetic overdose. The right epididimal tail was removed and used for spermatozoid collection. Sperm concentration, motility and viability (hypo-osmotic test) were assessed. The right testicles were fixed and routinely processed for obtaining hematoxylin and eosin stained histological sections. In these sections, the seminiferous tubule diameter, epithelial height and relative densities of the testicular structures were assessed by stereological methods. All data was compared by ANOVA with Tukey's post test, considering p<0.05 as significant. RESULTS Blood pressure in the HE group were similar WKY, and lower than H animals. Spermatozoid concentration had a 38% reduction in hypertensive rats when compared to controls while enalapril treatment restored normal concentration. Concerning spermatozoid motility and viability, no difference was found among the groups. Testicular vascular volumetric density was also altered in hypertensive group while HE animals were similar to controls. The seminiferous epithelium of HE animals showed the highest volumetric density, indicating a positive effect of enalapril in spermatogenesis. The analysis of seminiferous tubule diameter and epithelium height showed no significant difference among the studied groups. Table 1 presents all numerical data. CONCLUSIONS In the SHR model, hypertension induces testicular alterations both in seminiferous tubule and intratesticular vessels resulting in low spermatozoid concentration. Enalapril treatement partially protected the testicle from the hypertension-induced alterations, restoring normal spermatozoid production. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e838 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Gustavo Bechara Rio de Janeiro, Brazil More articles by this author Michele Simões Rio de Janeiro, Brazil More articles by this author Bruno Felix-Patricio Rio de Janeiro, Brazil More articles by this author Jorge Medeiros Rio de Janeiro, Brazil More articles by this author Bianca Gregório Rio de Janeiro, Brazil More articles by this author Diogo de Souza Rio de Janeiro, Brazil More articles by this author Waldemar Costa Rio de Janeiro, Brazil More articles by this author Francisco Sampaio Rio de Janeiro, Brazil More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Effect of uric acid on hypertension progression in spontaneously hypertensive rats

Aims We investigated the effects of soluble uric acid (UA) on the development of hypertension in spontaneously hypertensive rats (SHRs), using Wistar–Kyoto rats (WKY) as normotensive controls. Main methods UA was prepared freshly as a suspension in saline solution and administered twice daily, intraperitoneally, at a dose of 250 mg/kg body weight for five weeks to SHR-UA ( n = 7) and WKY-UA rats ( n = 5). Controls for both strains were injected with saline solution (WKY-C and SHR-C, n = 5 each). Blood pressure, determined by tail-cuff plethysmography, levels of urine and blood biochemical parameters were monitored weekly. Oxidative stress, renal cytokines mRNA levels and immune cells infiltration were determined at the end of the study. Key findings UA did not alter blood pressure in the WKY rats, but markedly prevented the development of hypertension in SHRs. Urine volume was significantly increased in the SHR-UA group. UA protected against renal oxidative stress as indicated by a decrease in MDA content in the SHR-UA group when compared to the SHR-C group; MDA content was unchanged in the WKY animals. Plasma antioxidant capacity decreased significantly in the SHR-UA animals when compared to the other three groups. There was a significant decrease in renal infiltrating lymphocytes in the SHR-UA treated animals. Changes in the expression of TNF-α, IL-2 and IL-6 were detected in the SHR-UA group. Significance We conclude that UA protects against progression of hypertension in SHR rats.

Angiotensin-(1–7) prevents diabetes-induced attenuation in PPAR-γ and catalase activities

The mechanisms by which angiotensin-(1–7) [Ang-(1–7)] exerts its beneficial effects on end-organ damage associated with diabetes and hypertension are not well understood. The purpose of this study was A) to compare the effects of apocynin with Ang-(1–7) on renal vascular dysfunction and NADPH oxidase activity in a combined model of diabetes and hypertension and B) to further determine whether chronic treatment with Ang-(1–7) can modulate renal catalase, and peroxisome proliferator activated receptor- γ (PPAR-γ) levels in streptozotocin-induced diabetes in both normotensive Wistar Kyoto rats (WKY) and in spontaneously hypertensive rats (SHR). Apocynin or Ang-(1–7) treatment for one month starting at the onset of diabetes similarly attenuated elevation of renal NADPH oxidase activity in the diabetic SHR kidney and reduced the degree of proteinuria and hyperglycemia, but had little or modest effect on reducing mean arterial pressure. Both drugs also attenuated the diabetes-induced increase in renal vascular responsiveness to endothelin-1. Induction of diabetes in WKY and SHR animals resulted in significantly reduced renal catalase activity and in PPAR-γ mRNA and protein levels. Treatment with Ang-(1–7) significantly prevented diabetes-induced reduction in catalase activity and the reduction in PPAR-γ mRNA and protein levels in both animal models. Taken together, these data suggest that activation of Ang-(1–7)-mediated signaling could be an effective way to prevent the elevation of NADPH oxidase activity and inhibition of PPAR-γ and catalase activities in diabetes and/or hypertension.

Hypertension affects the regulatory effect of nitric oxide on the respiratory chain

Nitric oxide (NO) synthesized from mitochondrial nitric oxide synthase (NOSmt) contributes to the regulation of oxidative phosphorylation by inhibiting ATP synthesis through the binding of NO to cytochrome c oxidase complex (complex IV) of the electron transport chain (ETC). We hypothesize that during hypertension the regulation of the ETC exerted by NO could be affected and could lead to a disruption in the mitochondrial energetic metabolism. Basal oxygen consumption during state 3 was increased in liver and kidney mitochondria from SHR of 1 and 7‐m.o. as compared with WKY animals of the same age. The sensitivity of complex IV to SNAP inhibition was lower in liver and kidney mitochondria from 7‐m.o. SHR as compared with mitochondria from WKY animals of the same age. Differential susceptibility to inhibition by SNAP was observed in complex IV activity from SHR rats of 7 months old for both organs. Activity of complex IV was inhibited with SNAP in a concentration‐dependent fashion in both WKY and SHR kidney and liver mitochondria from 1‐m.o. rats. The results suggest that hypertension lead to changes in ETC activity at the level of complex IV, which may be related with assembly defects of this complex during hypertension reported by others and contributes to mitochondrial dysfunction in kidney and liver during hypertension progression.

Dysregulation of cadherins in the intercalated disc of the spontaneously hypertensive stroke-prone rat

The structural integrity of cardiac cells is maintained by the Ca2+-dependent homophilic cell–cell adhesion of cadherins. N-cadherin is responsible for this adhesion under normal physiological conditions. The role of cadherins in adverse cardiac pathology is less clear. We studied the hearts of the stroke-prone spontaneously hypertensive (SHRSP) rat as a genetic model of cardiac hypertrophy and compared them to Wistar–Kyoto control animals. Western blotting of protein homogenates from 12-week old SHRSP animals indicated that similar levels of β, γ-, and α-catenin and T, N and R-cadherin were expressed in the control and SHRSP animals. However, dramatically higher levels of E-cadherin were detected in SHRSP animals compared to controls at 6, 12 and 18weeks of age. This was confirmed by quantitative Taqman PCR and immunohistochemistry. E-cadherin was located at the intercalated disc of the myocytes in co-localisation with connexin 43. Adenoviral overexpression of E-cadherin in rat H9c2 cells and primary rabbit myocytes resulted in a significant reduction in myocyte cell diameter and breadth. E-cadherin overexpression resulted in re-localisation of β-catenin to the cell surface particularly to cell–cell junctions. Subsequent immunohistochemistry of the hearts of WKY and SHRSP animals also revealed increased levels of β-catenin in the intercalated disc in the SHRSP compared to WKY. Therefore, remodelling of the intercalated disc in the hearts of SHRSP animals may contribute to the altered function observed in these animals.

Decreasing Superoxide Within The Nucleus Tractus Solitarius Partially Corrects Skeletal Muscle Mechanoreflex Overactivity In Hypertension

In hypertension, the blood pressure (BP) response to exercise is abnormally elevated. We have previously demonstrated that overactivity of the skeletal muscle mechanoreflex (MMR) plays a significant role in generating this exaggerated BP response to exercise. Yet the mechanisms underlying MMR overactivity remain unknown. Sensory information elicited by activation of the MMR is processed within the nucleus tractus solitarius (NTS) of the medulla oblongata. In normotensive rats, nitric oxide (NO) within the NTS is known to buffer MMR function. Recent evidence suggests the production of reactive oxygen species in the NTS, specifically superoxide (a NO scavenger), is increased in hypertension. Therefore, augmentations in superoxide production could reduce the NO available for biological activity. This may reduce the buffering capacity of NO in hypertension resulting in MMR overactivity. PURPOSE: To determine the effects of endogenously produced superoxide on MMR activity in male normotensive Wistar-Kyoto (WKY; n=4) and Spontaneously Hypertensive (SHR; n=5) rats. METHODS: The MMR was selectively activated by passively stretching hindlimb skeletal muscle before and after the microdialysis of the superoxide dismutase mimetic, tempol (30 μM) in the NTS. Superoxide dismutase is the endogenous enzyme responsible for the breakdown of superoxide. RESULTS: Activation of the MMR by stretch resulted in significantly larger increases in mean BP in SHR (58±5 mmHg) than WKY (22±3 mmHg). In both groups, dialysis of tempol reduced the BP response to stretch. Interestingly, the magnitude of the tempol-induced decrease in BP in response to MMR activation was larger in SHR (-24±6 mmHg) compared to WKY (-7±4 mmHg). Despite this larger effect, the stretch-induced augmentation in BP in SHR treated with tempol was greater than the BP increase elicited by stretch in untreated WKY. CONCLUSIONS: The results demonstrate that endogenously produced superoxide modulates MMR activity in both WKY and SHR animals. Further, the findings suggest that decreasing superoxide within the NTS can partially correct the exaggerated BP response to activation of the MMR in SHR. As such, the data are consistent with the concept that increases in superoxide production within the NTS contribute to MMR dysfunction in hypertension. Supported by HL-088422

Beta‐arrestin and vasomotor control in the spontaneously hypertensive rat

We tested the hypothesis that spontaneously hypertensive rats (SHR) exhibit reduced desensitization of the neuropeptide Y (NPY) Y1 receptor (Y1R) leading to altered hindlimb vasomotor control. ?‐arrestin 2 ( ?‐arr) is a key regulatory protein involved in the desensitization of the Y1R (as well as many other G‐protein coupled receptors (GPCRs)). Reduced ?‐arr would lead to less desensitization, and prolonged signal transduction. In vivo measurements of arterial pressure and femoral blood flow (Transonic) were measured in 7‐week old anaesthesized male SHR animals (n=5) and their genetic control (WKY; n=6) rats. Red vastus lateralis from the animals were analyzed for ?‐arr content by western blotting techniques. SHR content of ?‐arr was 1412 ± 827 units while ?‐arr content in the WKY animals was 3546 ± 898 units (p = 0.003; mean ± SD). These data are consistent with the 55% (p = 0.07) and 60% (p = 0.06) reductions in both hindlimb blood flow (ml/min) and conductance (ml/min/mmHg) to exogenous NPY (r = 0.77, p = 0.02 and r = 0.66, p = 0.05 respectively). β‐arr was also correlated with reductions in hindlimb flow to exogenous phenylephrine (r =0.76, p = 0.02). These data implicate a role for β‐arr in Y1R and alpha adrenergic receptor sensitization in hypertension. This work was supported by CIHR.

Effects of aglycone genistein in a rat experimental model of postmenopausal metabolic syndrome

Genistein aglycone, a soy derived isoflavone, has been demonstrated to be effective in reducing cardiovascular risk in postmenopausal women. We therefore investigated its effects in an experimental model of postmenopausal metabolic syndrome. Female spontaneously hypertensive obese rats (SHROB, n=40), a genetic model of syndrome X, and age-matched Wistar Kyoto (WKY, n=40) rats were used. A group of SHROB (n=20) and WKY (n=20) animals were ovariectomized (OVX). Four weeks after surgery all animals were randomized to receive either genistein (54 mg/human equivalent dose/day for 4 weeks), or vehicle. Body weight, food intake, systolic blood pressure (SBP), heart rate, plasma glucose, insulin resistance (HOMA-IR), total plasma cholesterol and triglycerides, and uterine weights were studied. Furthermore, we investigated acetylcholine- and sodium nitroprusside-induced relaxation of aortic rings as well as NG-L-arginine (L-NMA: 10-100 mM) induced vasoconstriction in phenylephrine-precontracted aortic segments. Liver expression of the peroxisome proliferator-activated receptor alpha (PPARA and gamma (PPARG was also assessed. OVX animals had a slight increase in SBP, body weight, insulin resistance, and plasma cholesterol. OVX-SHROB rats showed also impaired endothelial responses, blunted L-NMA induced contraction (L-NMA 100 mM, WKY=2.2+/-0.3 g/mg tissue; OVX-SHROB=1.1+/-0.4 g/mg tissue). Genistein treatment decreased SBP and plasma lipids, ameliorated endothelial dysfunction and insulin resistance, increased HDL cholesterol, and enhanced liver expression of PPARA and PPARG. Our data suggest that genistein is effective in ameliorating cardiovascular profiles in an experimental model of postmenopausal metabolic syndrome, attenuating the features of this disease. The effects of genistein are likely mediated by PPARA and PPARG receptors. This evidence would support the rationale for some pilot clinical trials using genistein in postmenopausal women affected by metabolic syndrome.

Upregulation of Heme Oxygenase-1 Combined with Increased Adiponectin Lowers Blood Pressure in Diabetic Spontaneously Hypertensive Rats through a Reduction in Endothelial Cell Dysfunction, Apoptosis and Oxidative Stress

This study was designed to investigate the effect of increased levels of HO-1 on hypertension exacerbated by diabetes. Diabetic spontaneously hypertensive rat (SHR) and WKY (control) animals were treated with streptozotocin (STZ) to induce diabetes and stannous chloride (SnCl2) to upregulate HO-1. Treatment with SnCl2 not only attenuated the increase of blood pressure (p<0.01), but also increased HO-1 protein content, HO activity and plasma adiponectin levels, decreased the levels of superoxide and 3-nitrotyrosine (NT), respectively. Reduction in oxidative stress resulted in the increased expression of Bcl-2 and AKT with a concomitant reduction in circulating endothelial cells (CEC) in the peripheral blood (p<0.005) and an improvement of femoral reactivity (response to acetylcholine). Thus induction of HO-1 accompanied with increased plasma adiponectin levels in diabetic hypertensive rats alters the phenotype through a reduction in oxidative stress, thereby permitting endothelial cells to maintain an anti-apoptotic environment and the restoration of endothelial responses thus preventing hypertension.

Effects of Music Composed by Mozart and Ligeti on Blood Pressure and Heart Rate Circadian Rhythms in Normotensive and Hypertensive Rats

There is continuing discussion on the effect of music (“Mozart effect”) on numerous functions in man and experimental animals. Radiotelemetry now allows one to monitor cardiovascular functions in freely‐moving unrestrained experimental animals. Radiotelemetry was used to monitor systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), and motor activity (MA) in male normotensive WKY and hypertensive SHR animals. Rats were synchronized to a 12 h light (L): 12 h dark (D) regimen in an isolated, ventilated, light‐controlled, sound‐isolated animal container. Music (Mozart, Symphony # 40; Ligeti, String Quartet # 2) were played for 2 h at 75 dB in the animal cabin starting at the onset of L or D in a cross‐over design. Data were collected every 5 min for 24 h under control conditions and during and after music. In addition, plasma concentrations of norepinephrine (NE) were determined in unrestrained animals at 3 h intervals over 24 h. In both WKY and SHR, highly significant circadian rhythms were obtained in SBP, DBP, HR, and MA under control conditions; HR was lower and BP higher in SHR than in WKY. NE was circadian rhythmic in both strains with higher values in D; the increase in NE with immobilization was much more pronounced in SHR than in WKY. The music of Mozart had no effect on either parameter in WKY, neither in L nor in D. In contrast, in SHR, the music of Mozart presented in L significantly decreased HR and left BP unaffected, leading to a small decrease in cardiac output. The music of Ligeti significantly increased BP both in L and in D and reflexively reduced HR in L, the effects being long‐lasting over 24 h. Interestingly, white noise at 75 dB had no effect at all on either function in both strains. The effects of both Mozart and Ligeti cannot be attributed to a stress reaction, as stress due to cage switch increased HR and BP both in WKY and SHR. The study clearly demonstrates that music of different character (tempo, rhythm, pitch, tonality) can modify cardiovascular functions in freely‐moving rats, with SHR being more sensitive than normotensive animals. The relative contribution of the characteristics of the two pieces of music, however, needs further evaluation.