Normotensive Rats Research Articles

Abstract P436: Increased West Nile Virus Infection And Pathology In The Spontaneously Hypertensive Rat

Introduction: West Nile virus (WNV), a mosquito-borne flavivirus, causes grave neuroinvasive disease and death, and has been reported in over 55,000 people in the US since 1999. Patients >55 years and those with hypertension are most at risk for WNV-associated mortality. Understanding how hypertension correlates with WNV morbidity and mortality may reduce the burden of this disease. Investigation of WNV in hypertensive people is limited to basic epidemiology. Without an animal model, understanding the causal relationship between hypertension and WNV-associated pathology remains elusive. Here, we tested a novel hypothesis that hypertension will promote WNV infection and pathology in a rodent model of age-dependent chronic hypertension, the spontaneously hypertensive rat (SHR). Methods: Male adult SHR and normotensive WKY rats were implanted with radiotelemetry transmitters for measurements of blood pressure and heart rate. Following baseline measurements, SHR and WKY rats (N=9/gp) were injected with WNV (1 X 10 4 PFU/ml, i.p.). Vehicle injection (PBS, i.p.) was performed in additional WKY and SHR (N=2-3/gp). Each rat was observed for clinical abnormalities, and body weight, blood pressure, and heart rate were measured daily. Rats were sacrificed on days 9 and 10 post-infection (PI). At endpoint, several tissues were processed for measurement of viral load by RT-qPCR and histopathology. Bone marrow and circulating immune cells (CD4 + , CD8 + , CD68 + ) were quantified at endpoint by flow cytometry. Results: One SHR rat developed neurological symptoms and was euthanized on day 4 PI. Viral load was significantly increased in the SHR kidney and spleen (P<0.001) in SHR compared to WKY rats. In addition, WNV-infection elevated heart rate in the SHR but not the WKY (P<0.0001). SHR also showed elevated circulating CD68 + monocytes (P<0.05), and a significant increase (P<0.05) in renal pathology was observed in the SHR following WNV infection. Conclusions: We demonstrate, for the first time, a positive interaction between high blood pressure and severity of WNV infection in a rodent model of chronic hypertension. Further studies are needed to elucidate the mechanisms of this interaction for new therapeutic targets of WNV disease.

Abstract 096: Effects Of Chronic Hypertension And Sex On Spatial Reference And Working Memory

Chronic hypertension is a primary risk factor of vascular dementia. The hippocampus is a brain region critical to learning and memory and is highly susceptible to hypoxia/ischemia. Here, we investigated how chronic hypertension affects two different types of memory function, and whether one sex is more susceptible to hypertension-induced memory impairment. Memory function in adult male and female SHR (spontaneously hypertensive rats) and normotensive Wistar rats was tested using two behavioral tasks (n=6/group). The radial arm maze (RAM) tested reference memory that is largely hippocampal-dependent by measuring the time it took to retrieve rewards from three baited arms during daily 10 min sessions. A continuous y maze task was used to calculate alternation index and determine working memory that is cortico-hippocampal-dependent. Data are mean±SEM and comparisons made via a two-way ANOVA with a post-hoc Tukey test. In the RAM task, female rats had steeper learning curves than males as they completed the task in less time with each session (Fig 1). There was a significant interaction between sex and hypertension in the y maze task (F (1,20) =13.26, p=0.002). Working memory was impaired in female SHR, with a lower alternation index (index=0.60±0.03) than Wistar rats (index=0.74±0.03). However, male SHR that had a higher alternation index of 0.75±0.02 compared to 0.58±0.6 in male Wistar rats. Overall, females had stronger reference memory than males regardless of hypertension. Working memory was differentially affected in male and female SHR, suggesting sex differences in the susceptibility of different brain regions and types of memory to hypertension-induced dysfunction.

Abstract P104: EXAMINING THE EFFECTS OF FOLLISTATIN ON CONTRACTION OF VESSELS FROM NORMOTENSIVE AND HYPERTENSIVE RATS

The lab has previously shown that follistatin (FST), a glycoprotein inhibitor of activins, reduced blood pressure in the Spontaneously Hypertensive Rat (SHR) model of Essential Hypertension. Short-term exposure (30 minutes) to FST also reduced vessel contraction induced by potassium (KCl). This study aims to illustrate the mechanisms through which FST inhibits potassium-induced contraction in SHR and normotensive (WKY) rats. Function of SHR or WKY resistance mesenteric arteries was tested in response to KCl and ion channel modulators using wire myography. Cultures of primary smooth muscle cells (SMC) were also established from these vessels using cell explant technique. The calcium sensor dye Fluo-4 AM was used to examine calcium influx on a cellular level. To test whether FST effects were due to activin neutralization or activin-receptor inhibition, neutralizing antibodies against activin A and B or an activin receptor inhibitor (SB 431542) were used, respectively. Only activin A neutralization in the SHR reduced KCl-induced contraction similarly to FST. Activin receptor inhibition also reduced KCl constriction similarly to FST. When directly stimulated with Activin A, both WKY and SHR vessels displayed augmented KCl contraction compared to controls but the effect was more pronounced in the SHR. Preliminary Fluo-4 results showed that FST decreased KCl-induced calcium influx in SMC. Since activin A was shown to increase L-type voltage-gated Ca2+channel activity, an agonist (FPL 64176) of this channel was used to induce contraction. Although FST reduced KCl-induced contraction, it did not affect FPL-induced contraction in either SHR or WKY. Thus, Activin A neutralization reproduces FST reduction of KCl-induced vessel contraction. FST did not reduce FPL-induced contraction, suggesting that its inhibition of KCl-induced contraction is not through effects on this channel but rather an alternate Ca2+ or K-ATP channel.

Pregnancy hypertension-associated endothelial dysfunction is attenuated by isoflurane anesthesia: Evidence of protective effect related to increases in nitric oxide

AimsPregnancy hypertension-induced endothelial dysfunction associated with impairment of nitric oxide (NO) bioavailability and hemodynamic derangements is a challenging for urgent procedures requiring maternal anesthesia. The volatile anesthetic isoflurane has demonstrated NO-associated protective effects. However, this isoflurane-induced effect is still unclear in pregnancy hypertension. Therefore, the present study examined the potential protective effects of isoflurane anesthesia on endothelial dysfunction and hemodynamic changes induced by hypertensive pregnancy associated with fetal and placental growth restrictions. Materials and methodsAnimals were distributed into four groups: normotensive pregnant rats (Preg), anesthetized pregnant rats (Preg+Iso), hypertensive pregnant rats (HTN-Preg), and anesthetized hypertensive pregnant rats (HTN-Preg+Iso). Systolic and diastolic pressures, mean arterial pressure (MAP), heart rate, fetal and placental weights, vascular contraction, endothelium-derived NO-dependent vasodilation, and NO levels were assessed. The vascular endothelial growth factor (VEGF) levels and endothelial NO synthase (eNOS) Serine (1177) phosphorylation (p-eNOS) expression were also examined. Key findingsIsoflurane produced more expressive hypotensive effects in the HTN-Preg+Iso versus Preg+Iso group, with respective reductions in MAP by 50 ± 13 versus 25 ± 4 mmHg (P < 0.05). Also, HTN-Preg+Iso compared to the HTN-Preg group showed (respectively) preventions against the weight loss of the fetuses (4.0 ± 0.6 versus 2.8 ± 0.6 g, P < 0.05) and placentas (0.37 ± 0.06 versus 0.30 ± 0.06 mg, P < 0.05), hyper-reactive vasocontraction response (1.8 ± 0.4 versus 2.8 ± 0.6 g, P < 0.05), impaired endothelium-derived NO-dependent vasodilation (84 ± 8 versus 50 ± 17 %, P < 0.05), reduced VEGF levels (147 ± 46 versus 25 ± 13 pg/mL, P < 0.05), and decreased p-eNOS expression (0.24 ± 0.07 versus 0.09 ± 0.05 arbitrary units, P < 0.05). SignificanceIsoflurane anesthesia protects maternal endothelial function in pregnancy hypertension, and possibly endothelium-derived NO is involved.

Decreased retinal and choroidal endothelial surface molecules in spontaneously hypertensive rats

Hypertension is associated with changes in the retina and choroid, with resulting consequences of increased vascular permeability and microhemorrhages. To date, very little information is available regarding the changes in the retinal and choroidal endothelial surface layer. In this study, we have examined changes in protein expression of several molecules including platelet endothelial cell adhesion molecule-1 (PECAM-1), vascular endothelial cadherin (VE-cadherin), glypican-1, and syndecan-1, in spontaneously hypertensive rats (SHR) compared to control normotensive Wistar Kyoto (WKY) rats. In male SHR vs WKY rat retinas, decreases were found for VE-cadherin and syndecan-1; whereas in female retinas, decreases were found for PECAM-1, glypican-1, and syndecan-1. In male SHR vs WKY rat choroid, we found an increase in glypican-1, but choroidal syndecan-1 was decreased in SHR in both males and females. Therefore, decreases in SHR of both retinal and choroidal syndecan-1 were found in both males and females. These losses of syndecan-1 were accompanied by an increase in plasma levels of the proteoglycan, indicating possible systemic endothelial shedding. In contrast, plasma levels of glypican-1 decreased. Interestingly, in normotensive WKY rats, retinal levels of all four endothelial surface molecules were higher in females than in males, in some cases, by substantial amounts. In summary, a number of changes occur in endothelial surface molecules in SHR, with some changes being sex-dependent; it is possible that the loss of these molecules contributes to the vascular dysfunction that occurs in hypertensive retina and choroid.

Impaired renal autoregulation and pressure-natriuresis: any role in the development of heart failure in normotensive and angiotensin II-dependent hypertensive rats?

The aim of the present study was to assess the autoregulatory capacity of renal blood flow (RBF) and of the pressure-natriuresis characteristics in the early phase of heart failure (HF) in rats, normotensive and with angiotensin II (ANG II)-dependent hypertension. Ren-2 transgenic rats (TGR) were employed as a model of ANG II-dependent hypertension. HF was induced by creating the aorto-caval fistula (ACF). One week after ACF creation or sham-operation, the animals were prepared for studies evaluating in vivo RBF autoregulatory capacity and the pressure-natriuresis characteristics after stepwise changes in renal arterial pressure (RAP) induced by aortic clamping. In ACF TGR the basal mean arterial pressure, RBF, urine flow (UF), and absolute sodium excretion (UNaV) were all significantly lower tha n in sham-operated TGR. In the latter, reductions in renal arterial pressure (RAP) significantly decreased RBF whereas in ACF TGR they did not change. Stepwise reductions in RAP resulted in marked decreases in UF and UNaV in sham-operated as well as in ACF TGR, however, these decreases were significantly greater in the former. Our data show that compared with sham-operated TGR, ACF TGR displayed well-maintained RBF autoregulatory capacity and improved slope of the pressure-natriuresis relationship. Thus, even though in the very early HF stage renal dysfunction was demonstrable, in the HF model of ANG II-dependent hypertensive rat such dysfunction and the subsequent HF decompensation cannot be simply ascribed to impaired renal autoregulation and pressure-natriuresis relationship.

Effects of aurantiamide on a rat model of renovascular arterial hypertension.

Asperglaucide (ASP) is an aurantiamide, an effective constituent of purslane (Portulaca oleracea L.), a safe to eat greenery. Effects of ASP on endothelial function, endothelial nitric oxide synthase (eNOS) expression, vascular fluidity, renal and vascular reactive oxygen, and nitrogen species (ROS/RNS) production was examined in the two-kidney one-clip (2K-1C) rat model of renovascular arterial hypertension. ASP toxicity, dose dependent eNOS gene expression and protein levels were also analyzed in human umbilical vein endothelial cells (HUVEC). The 2K-1C model of hypertension was created via surgery and mean blood pressure (MBP) was measured by tail-cuff method during four weeks of ASP treatment. Erythrocyte deformability was monitored by rotational ektacytometry, while vascular constrictor and dilator responses were determined in organ baths. eNOS gene expression and protein levels were assessed in thoracic aorta and HUVEC. MBP was significantly decreased in hypertensive rats treated with ASP. Endothelium dependent vascular dilator and constrictor responses were also considerably improved following ASP treatment. There was a notable increase in red blood cell deformability in hypertensive rats treated with ASP as compared to hypertensive rats alone. A significant increase was observed in eNOS gene expression and protein levels in both normotensive and hypertensive rats treated with ASP. Treatment of HUVEC with 3µM ASP notably increased eNOS mRNA and protein levels. In conclusion, ASP lowered blood pressure, improved endothelium-mediated relaxation, decreased renovascular ROS/RNS production in hypertensive rats. ASP also increased eNOS protein expression in aorta and HUVEC at nontoxic doses. ASP may have future potential as an anti-hypertensive agent.

Sodium Nitrite Attenuates Reduced Activity of Vascular Matrix Metalloproteinase-2 and Vascular Hyper-Reactivity and Increased Systolic Blood Pressure Induced by the Placental Ischemia Model of Preeclampsia in Anesthetized Rats.

Preeclampsia is a maternal hypertension disorder associated with vascular dysfunction and fetal and placental growth restrictions. Placental ischemia is suggested as the primary trigger of preeclampsia-associated impairments of both endothelium-derived nitric oxide (NO) and the vascular activity of extracellular matrix metalloproteinase-2 (MMP-2). Reduced uteroplacental perfusion pressure (RUPP) is a placental ischemia model of preeclampsia. Reduction of sodium nitrite to NO may occur during ischemic conditions. However, sodium nitrite effects in the RUPP model of preeclampsia have not yet been investigated. Pregnant rats were divided into four groups: normotensive pregnant rats (Norm-Preg), pregnant rats treated with sodium nitrite (Preg + Nitrite), preeclamptic rats (RUPP), and preeclamptic rats treated with sodium nitrite (RUPP + Nitrite). Maternal blood pressure and fetal and placental parameters were recorded. Vascular function, circulating NO metabolites, and the gelatinolytic activity of vascular MMP-2 were also examined. Sodium nitrite attenuates increased blood pressure, prevents fetal and placental weight loss, counteracts vascular hyper-reactivity, and partially restores NO metabolites and MMP-2 activity. In conclusion, sodium nitrite reduction to NO may occur during RUPP-induced placental ischemia, thereby attenuating increased blood pressure, fetal and placental growth restriction, and vascular hyper-reactivity associated with preeclampsia and possibly restoring NO and MMP-2 activity, which underlie the blood pressure-lowering effects.

Acute nitric oxide synthase inhibition induces greater increases in blood pressure in female versus male Wistar Kyoto rats.

Nitric oxide (NO) contributes to blood pressure (BP) regulation via its vasodilatory and anti-inflammatory properties. We and others previously reported sex differences in BP in normotensive and hypertensive rat models where females have lower BP than age-matched males. As females are known to have greater NO bioavailability than age-matched males, the current study was designed to test the hypothesis that anesthetized female normotensive Wistar Kyoto rats (WKY) are more responsive to acute NOS inhibition-induced increases in BP compared to male WKY. Twelve-week-old male and female WKY were randomized to infusion of the nonspecific NOS inhibitor NG -nitro-L-arginine methyl ester (L-NAME, 1 mg/kg/min) or selective NOS1 inhibition with vinyl-L-NIO (VNIO, 0.5 mg/kg/min) for 60 min. Mean arterial BP, glomerular filtration rate (GFR), urine volume, and electrolyte excretion were assessed before, and during L-NAME or VNIO infusion. L-NAME and VNIO significantly increased BP in both sexes; however, the increase in BP with L-NAME infusion was greater in females versus males compared to baseline BP values. Acute infusion of neither L-NAME nor VNIO for 60 min altered GFR in either sex. However, urine volume, sodium, chloride and potassium excretion levels increased comparably in male and female WKY with L-NAME and VNIO infusion. Our findings suggest sex differences in BP responses to acute non-isoform-specific NOS inhibition in WKY, with females being more responsive to L-NAME-induced elevations in BP relative to male WKY. However, sex differences in the BP response did not coincide with sex differences in renal hemodynamic responses to acute NOS inhibition.

Functional symmetry of the aortic baroreflex in female spontaneously hypertensive rats.

Altered baroreflex function is well documented in hypertension; however, the female sex remains far less studied compared with males. We have previously demonstrated a left-sided dominance in the expression of aortic baroreflex function in male spontaneously hypertensive rats (SHRs) and normotensive rats of either sex. If lateralization in aortic baroreflex function extends to hypertensive female rats remains undetermined. This study, therefore, assessed the contribution of left and right aortic baroreceptor afferents to baroreflex modulation in female SHRs. Anesthetized female SHRs (total n = 9) were prepared for left, right and bilateral aortic depressor nerve (ADN) stimulation (1-40 Hz, 0.2 ms, 0.4 mA for 20 s) and measurement of reflex mean arterial pressure (MAP), heart rate (HR), mesenteric vascular resistance (MVR) and femoral vascular resistance (FVR). All rats were also matched for the diestrus phase of the estrus cycle. Reflex (%) reductions in MAP, HR, MVR and FVR were comparable for both left-sided and right-sided stimulation. Bilateral stimulation evoked slightly larger ( P = 0.03) reductions in MVR compared with right-sided stimulation; however, all other reflex hemodynamic measures were similar to both left-sided and right-sided stimulation. These data show that female SHRs, unlike male SHRs, express similar central integration of left versus right aortic baroreceptor afferent input and thus show no laterization in the aortic baroreflex during hypertension. Marginal increases in mesenteric vasodilation following bilateral activation of the aortic baroreceptor afferents drive no superior depressor responses beyond that of the unilateral stimulation. Clinically, unilateral targeting of the left or right aortic baroreceptor afferents may provide adequate reductions in blood pressure in female hypertensive patients.

Age-Dependent Changes in the Relationships between Traits Associated with the Pathogenesis of Stress-Sensitive Hypertension in ISIAH Rats

Hypertension is one of the most significant risk factors for many cardiovascular diseases. At different stages of hypertension development, various pathophysiological processes can play a key role in the manifestation of the hypertensive phenotype and of comorbid conditions. Accordingly, it is thought that when diagnosing and choosing a strategy for treating hypertension, it is necessary to take into account age, the stage of disorder development, comorbidities, and effects of emotional–psychosocial factors. Nonetheless, such an approach to choosing a treatment strategy is hampered by incomplete knowledge about details of age-related associations between the numerous features that may contribute to the manifestation of the hypertensive phenotype. Here, we used two groups of male F2(ISIAHxWAG) hybrids of different ages, obtained by crossing hypertensive ISIAH rats (simulating stress-sensitive arterial hypertension) and normotensive WAG rats. By principal component analysis, the relationships among 21 morphological, physiological, and behavioral traits were examined. It was shown that the development of stress-sensitive hypertension in ISIAH rats is accompanied not only by an age-dependent (FDR &lt; 5%) persistent increase in basal blood pressure but also by a decrease in the response to stress and by an increase in anxiety. The plasma corticosterone concentration at rest and its increase during short-term restraint stress in a group of young rats did not have a straightforward relationship with the other analyzed traits. Nonetheless, in older animals, such associations were found. Thus, the study revealed age-dependent relationships between the key features that determine hypertension manifestation in ISIAH rats. Our results may be useful for designing therapeutic strategies against stress-sensitive hypertension, taking into account the patients’ age.

The diuretic effect of ethyl acetate fractions of Artocarpus altilis, Artocarpus champeden, and Artocarpus heterophyllus leaves in normotensive Wistar rats

BackgroundArtocarpus altilis, A. Champeden, and Artocarpus heterophylus are popular species in Indonesia, and are commonly used as traditional medicine. ObjectiveThis study aims to evaluate the diuretic effects of the ethyl acetate fraction of these three species on normotensive Wistar rats. MethodsThe ethyl acetate fraction was prepared by a liquid–liquid extraction method. To evaluate diuretic effects, the sixty rats were divided into normal (distilled water), negative (4.5% NaCl), positive control (furosemide 5 mg/kg), and the testing groups. The testing groups were orally given the ethyl acetate fraction of A. altilis, Artocarpus champeden, and A. heterophylus at three dose levels of 25, 50, and 100 mg/kg. All animals were orally given 4.5% NaCl at a dose of 2 mL/200 g except the normal group; then the animals were given drugs according to group doses. Urine volume and electrolyte levels produced by the testing groups were compared to those of the control group. The concentration and ratio of ions were calculated to determine the natriuretic and carbonic anhydrase activities. Results: The ethyl acetate fractions of the three Artocarpus species at 100 mg/kg dose were more active than the standard furosemide (p < 0.05) to increase urinary excretion. Furthermore, at doses of 50 and 100 mg/kg, the fraction significantly increased the excretion of Na+, K+, and Cl- ions more than the standard (p < 0.05). The testing groups showed good natriuretic and carbonic anhydrase activities. ConclusionsThe ethyl acetate fraction of A. altilis, A. champeden, and A. heterophylus leaves performed good diuretic and natriuretic activities. Therefore, the fractions can be considered as potential natural diuretic medicines.

Loss of IP3R-BKCa Coupling Is Involved in Vascular Remodeling in Spontaneously Hypertensive Rats.

Mechanisms by which BKCa (large-conductance calcium-sensitive potassium) channels are involved in vascular remodeling in hypertension are not fully understood. Vascular smooth muscle cell (VSMC) proliferation and vascular morphology were compared between hypertensive and normotensive rats. BKCa channel activity, protein expression, and interaction with IP3R (inositol 1,4,5-trisphosphate receptor) were examined using patch clamp, Western blot analysis, and coimmunoprecipitation. On inside-out patches of VSMCs, the Ca2+-sensitivity and voltage-dependence of BKCa channels were similar between hypertensive and normotensive rats. In whole-cell patch clamp configuration, treatment of cells with the IP3R agonist, Adenophostin A (AdA), significantly increased BKCa channel currents in VSMCs of both strains of rats, suggesting IP3R-BKCa coupling; however, the AdA-induced increases in BKCa currents were attenuated in VSMCs of hypertensive rats, indicating possible IP3R-BKCa decoupling, causing BKCa dysfunction. Co-immunoprecipitation and Western blot analysis demonstrated that BKCa and IP3R proteins were associated together in VSMCs; however, the association of BKCa and IP3R proteins was dramatically reduced in VSMCs of hypertensive rats. Genetic disruption of IP3R-BKCa coupling using junctophilin-2 shRNA dramatically augmented Ang II-induced proliferation in VSMCs of normotensive rats. Subcutaneous infusion of NS1619, a BKCa opener, to reverse BKCa dysfunction caused by IP3R-BKCa decoupling significantly attenuated vascular hypertrophy in hypertensive rats. In summary, the data from this study demonstrate that loss of IP3R-BKCa coupling in VSMCs induces BKCa channel dysfunction, enhances VSMC proliferation, and thus, may contribute to vascular hypertrophy in hypertension.

Antioxidant activity enhancement and oxidative damage inhibition by Lagenaria breviflora fruit and Xanthosoma sagittifolium corm in hypertensive Wistar rats.

Cardiovascular diseases are the leading causes of mortality in the world today with hypertension being the major clinical presentation of these diseases. This study assessed the anti-hypertensive effects of Lagenaria breviflora whole fruit and Xanthsoma sagittifolium corms in experimentally inudced hypertensive Wistar rats. The ability of the plants to ameliorate oxidative damage accompanying hypertension was evaluated using changes in oxidative stress markers as well as monitoring of cardiovascular parameters. Hypertension was induced by intraperitoneal injection of DOCA salt twice weekly and daily inclusion of NaCl (1%) in drinking water. Methanol extracts of L.breviflora or X. sagittifolium was administered to hypertensive rats for 35 days and the outcome was compared to hypertensive rats administred with lisinopril or hydrochlorothiazide and a group of normotensive rats (control). Systolic, diastolic and mean arterial pressures were determined on day 34 and blood sample collected on day 35. The rats were thereafter humanely sacrificed, and organs were harvested. This study showed that the extracts lowered blood pressure, free protein thiols but increased toal protein, gluthathione peroxidase, reduced glutathione, glutathione S-transferase, catalase and nitric oxide in the heart, kidney and liver compared to untreated hypertensive rats. However, malondialdehyde levels and hydrogen peroxide activities were reduced. L. breviflora fruit and X. sagittifloium corm exhibited antihypertensive properties and ameliorate oxidative damage associated with hypertension by enhancing the antioxidant defense sysyem and inhibiting generation of free radicals.

Pathogenetic characteristics of the hormonal profile in rats subjected to restraint stress of different duration

The aim of the work is to ascertain the character of changes in the hormonal profile (concentrations of corticosterone, insulin, and adrenocorticotropic hormone) in conjunction with metabolic alterations and elevated blood pressure, which are induced in rats by restraint stress at 6th, 15th and 21st weeks of environmental space restriction.&#x0D; Materials and methods. A total of 55 normotensive male Wistar rats, aged 6–10 months, were assigned into 4 experimental groups (1 – intact control (10 rats); 2, 3 and 4 (15 rats each exposed to restricted space allowance)). All the animals were subjected to blood pressure (BP), blood glucose level and body weight measurements twice: at the stage of forming groups and at the 6th, 15th and 21st weeks. Plasma hormone concentrations (insulin, corticosterone, and ACTH) were examined by the immunoenzymatic method using commercial kits (Monobind, USA).&#x0D; Results. The body weight of the animals was significantly reduced by 20.72 % after 6 weeks of space allowance restriction, it was restored to baselines by the 15th week and exceeded control values by 26.1 % at the 21st week. BP levels showed an increasing trend, a dynamic increase in systolic pressure by 7 %, 17 % and 26 % was detected, respectively, as well as diastolic from the 15th week to the 21st week by 21.4 % and 37.0 %, respectively. Glucose concentration was within the euglycemic range. Changes in the hormonal profile showed an increase in the concentration of ACTH by more than 50 % and a decrease in insulin – by 34 % at the 6th week with a subsequent twofold decrease in the insulin concentration (at week 15) and a further more than twofold increase in ACTH at the 21st week. As for changes in the concentration of corticosterone, a peak increase of 3.77 times was noticed at the 15th week, followed by a decrease and restoration to the normative values by the 21st week.&#x0D; Conclusions. Even minor and unremarkable continuously acting stressors, which cannot be coped, become important triggers for hormonal profile and carbohydrate metabolism alterations as well as for a persistent increase in blood pressure, which manifest first by hypoinsulinemia, an increase in the level of ACTH, and a constant concentration of corticosterone. Long-term stress exposure contributes to a transient “peak” increase in the corticosterone level, a significant increase in insulin and a sustained increase in ACTH. Multidirectional changes in the levels of the studied hormones occur amidst a gradual increase in blood pressure and a stable increase in the level of glycemia.

The treatment with sGC stimulator improves survival of hypertensive rats in response to volume-overload induced by aorto-caval fistula

Heart failure (HF) has been declared as global pandemic and current therapies are still ineffective, especially in patients that develop concurrent cardio-renal syndrome. Considerable attention has been focused on the nitric oxide (NO)/soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway. In the current study, we aimed to investigate the effectiveness of sGC stimulator (BAY41-8543) with the same mode of action as vericiguat, for the treatment of heart failure (HF) with cardio-renal syndrome. As a model, we chose heterozygous Ren-2 transgenic rats (TGR), with high-output heart failure, induced by aorto-caval fistula (ACF). The rats were subjected into three experimental protocols to evaluate short-term effects of the treatment, impact on blood pressure, and finally the long-term survival lasting 210 days. As control groups, we used hypertensive sham TGR and normotensive sham HanSD rats. We have shown that the sGC stimulator effectively increased the survival of rats with HF in comparison to untreated animals. After 60 days of sGC stimulator treatment, the survival was still 50% compared to 8% in the untreated rats. One-week treatment with sGC stimulator increased the excretion of cGMP in ACF TGR (109 ± 28 nnmol/12 h), but the ACE inhibitor decreased it (-63 ± 21 nnmol/12 h). Moreover, sGC stimulator caused a decrease in SBP, but this effect was only temporary (day 0: 117 ± 3; day 2: 108 ± 1; day 14: 124 ± 2 mmHg). These results support the concept that sGC stimulators might represent a valuable class of drugs to battle heart failure especially with cardio-renal syndrome, but further studies are necessary.

The Phthalic Selenoanhydride Decreases Rat Blood Pressure and Tension of Isolated Mesenteric, Femoral and Renal Arteries.

Phthalic selenoanhydride (R-Se) solved in physiological buffer releases various reactive selenium species including H2Se. It is a potential compound for Se supplementation which exerts several biological effects, but its effect on the cardiovascular system is still unknown. Therefore, herein we aimed to study how R-Se affects rat hemodynamic parameters and vasoactive properties in isolated arteries. The right jugular vein of anesthetized Wistar male rats was cannulated for IV administration of R-Se. The arterial pulse waveform (APW) was detected by cannulation of the left carotid artery, enabling the evaluation of 35 parameters. R-Se (1-2 µmol kg-1), but not phthalic anhydride or phthalic thioanhydride, transiently modulated most of the APW parameters including a decrease in systolic and diastolic blood pressure, heart rate, dP/dtmax relative level, or anacrotic/dicrotic notches, whereas systolic area, dP/dtmin delay, dP/dtd delay, anacrotic notch relative level or its delay increased. R-Se (~10-100 µmol L-1) significantly decreased the tension of precontracted mesenteric, femoral, and renal arteries, whereas it showed a moderate vasorelaxation effect on thoracic aorta isolated from normotensive Wistar rats. The results imply that R-Se acts on vascular smooth muscle cells, which might underlie the effects of R-Se on the rat hemodynamic parameters.

Genistein increases blood pressure in pre-treated normotensive rats

Genistein increases blood pressure in pre-treated normotensive rats

#4127 MODULATION OF BLOOD PRESSURE THROUGH MICROBIOME EXCHANGE BETWEEN MILAN NORMOTENSIVE AND HYPERTENSIVE STRAINS OF RATS

Abstract Background and Aims Hypertension is one of the major health problems contributing to the development of cardiovascular diseases. In contrast to essential hypertension, which often displays complex pathogenesis due to multifactorial aetiology, several monogenic forms of hypertension are caused by mutations in genes associated with renal salt handling. Thus, studies on monogenic forms of hypertension could hold potential for novel therapeutic approaches for essential hypertension. Recently, increasing numbers of studies have demonstrated the alteration of the gut microbiome in pathological states including hypertension. These observations suggest the involvement of the intestinal microbiome in the development and/or maintenance of hypertension. A reciprocal congenic strain of Milan hypertensive rat (NA rat), harbouring a missense mutation in the gene encoding the alpha subunit of the membrane-skeletal protein adducin (Add1), develops hypertension starting from 3 months after birth. Preliminary studies on NA rats and its littermate Milan normotensive (MN) rats showed diverse expression patterns of renal sodium transporters/ion channels in two strains of rats, indicating a putative role of altered renal salt handling on the enhanced blood pressure in NA rats (unpublished data). Based on this background, the aim of this study was to investigate a possible connection between the gut microbiome and blood pressure phenotypes in these two strains. Furthermore, we evaluated whether the exchange of faeces between the two strains could transfer the phenotypes through the gut microbiome. Finally, mechanisms underlying the altered phenotype after microbiome exchange were investigated. Method Hypertensive NA rats and normotensive MN rats were subjected to ‘homogenization (HOM)’ of the microbiome after birth, which consisted of the exchange of bedding containing faeces from either strain, followed by co-housing of MN and NA rats in the same cage (MN-HOM and NA-HOM groups). For the baseline (BSL) condition, rats were homogenized within the same strain (MN-BSL and NA-BSL). At the age of 5 months, blood pressure measurement was performed using a non-invasive tail-cuff BP-2000 Blood Pressure Analysis system. Faeces from each rat were collected for microbiota metataxonomic analysis using next generation sequencing of 16S ribosome encoding DNA. At the end of the treatment, rats were sacrificed for the collections of blood and organs to assess the expressions of genes involved in renal salt reabsorption. Results Systolic blood pressure (SBP) in MN-BSL was averaged at 143.6 mmHg, while NA-BSL showed average SBP 163.3 mmHg, confirming the hypertensive phenotype in NA rats at baseline (P&amp;lt;0.001). Interestingly, MN-HOM showed a significantly enhanced SBP compared to MN-BSL, reaching 153.5 mmHg (P = 0.005). On the other hand, the average SBP of NA-HOM was163.7 mmHg, indicating that homogenization did not significantly impact blood pressure in NA rats. Although the MN-HOM group showed significantly increased SBP compared with MN-BSL group, the average SBP of MN-HOM was still significantly lower than both the NA-BSL and NA-HOM groups. Different gut microbiota compositions were observed in the two strains of rats at baseline, and HOM altered both. Conclusion We have demonstrated that the hypertensive phenotype in NA rats was transferred to normotensive MN rats through the exchange of gut microbiota, indicating that the intestinal microbiota and/or metabolites derived therefrom could eventually modulate blood pressure. Further studies including immunoblotting as well as uremic toxin analyses are required to unveil the molecular mechanisms by which the gut microbiome modulates blood pressure.

Methyl Palmitate Modulated NMDA-Induced Cerebral Hyperemia in Hypertensive Rats

N-methyl-D-aspartate (NMDA) receptors were found to be dysfunctional in hypertensive rats. Methyl palmitate (MP) has been shown to diminish the nicotine-induced increase in blood flow in the brainstem. The aim of this study was to determine how MP modulated NMDA-induced increased regional cerebral blood flow (rCBF) in normotensive (WKY), spontaneously hypertensive (SHR), and renovascular hypertensive (RHR) rats. The increase in rCBF after the topical application of experimental drugs was measured using laser Doppler flowmetry. Topical NMDA application induced an MK-801-sensitive increase in rCBF in anesthetized WKY rats, which was inhibited by MP pretreatments. This inhibition was prevented by pretreatment with chelerythrine (a PKC inhibitor). The NMDA-induced increase in rCBF was also inhibited by the PKC activator in a concentration-dependent manner. Neither MP nor MK-801 affected the increase in rCBF induced by the topical application of acetylcholine or sodium nitroprusside. Topical application of MP to the parietal cortex of SHRs, on the other hand, increased basal rCBF slightly but significantly. MP enhanced the NMDA-induced increase in rCBF in SHRs and RHRs. These results suggested that MP had a dual effect on the modulation of rCBF. MP appears to play a significant physiological role in CBF regulation.