Pomegranate peel extract attenuates oxidative stress by decreasing coronary angiotensin-converting enzyme (ACE) activity in hypertensive female rats.

Based on the antioxidant properties of pomegranate, this study was designed to investigate the effects of pomegranate peel extract on damage associated with hypertension and aging in a spontaneously hypertensive rat (SHR) model. The influence of pomegranate consumption was examined on systolic blood pressure (SBP), angiotensin-converting enzyme (ACE) coronary activity, oxidative stress, and vascular morphology. Four- or 28-wk-old SHR model rats were treated for 30 d, with terminal experimental animal age being 8 and 32 wk, respectively, with either pomegranate extract (SHR-PG) or filtered water (SHR). Data showed significant reduction in SBP and coronary ACE activity in both age groups. The levels of superoxide anion, a measure of oxidative stress, were significantly lower in animals in the SHR-PG group compared to SHR alone. Coronary morphology demonstrated total increases in vascular wall areas were in the SHR group, and pomegranate peel extract diminished this effect. Pomegranate peel extract consumption conferred protection against hypertension in the SHR model. This finding was demonstrated by marked reduction in coronary ACE activity, oxidative stress, and vascular remodelling. In addition, treatment was able to reduce SBP in both groups. Evidence indicates that the use of pomegranate peel extract may prove beneficial in alleviating coronary heart disease.

Pomegranate Extract Enhances Endothelium-Dependent Coronary Relaxation in Isolated Perfused Hearts from Spontaneously Hypertensive Ovariectomized Rats.

Decline in estrogen levels promotes endothelial dysfunction and, consequently, the most prevalent cardiovascular diseases in menopausal women. The use of natural therapies such as pomegranate can change these results. Pomegranate [Punica granatum L. (Punicaceae)] is widely used as a phytotherapeutic agent worldwide, including in Brazil. We hypothesized that treatment with pomegranate hydroalcoholic extract (PHE) would improve coronary vascular reactivity and cardiovascular parameters. At the beginning of treatment, spontaneously hypertensive female rats were divided into Sham and ovariectomized (OVX) groups, which received pomegranate extract (PHE) (250 mg/kg) or filtered water (V) for 30 days by gavage. Systolic blood pressure was measured by tail plethysmography. After euthanasia, the heart was removed and coronary vascular reactivity was assessed by Langendorff retrograde perfusion technique. A dose-response curve for bradykinin was performed, followed by L-NAME inhibition. The protein expression of p-eNOS Ser1177, p-eNOS Thr495, total eNOS, p-AKT Ser473, total AKT, SOD-2, and catalase was quantified by Western blotting. The detection of coronary superoxide was performed using the protocol of dihydroethidium (DHE) staining Plasma nitrite measurement was analyzed by Griess method. Systolic blood pressure increased in both Sham-V and OVX-V groups, whereas it was reduced after treatment in Sham-PHE and OVX-PHE groups. The baseline coronary perfusion pressure was reduced in the Sham-PHE group. The relaxation was significantly higher in the treated group, and L-NAME attenuated the relaxation in all groups. The treatment has not changed p-eNOS (Ser1177), total eNOS, p-AKT (Ser473) and total AKT in any groups. However, in Sham and OVX group the treatment reduced the p-eNOS (Thr495) and SOD-2. The ovariectomy promoted an increasing in the superoxide anion levels and the treatment was able to prevent this elevation and reducing oxidative stress. Moreover, the treatment prevented the decreasing in plasmatic nitrite. We observed a reduction in total cholesterol and LDL in the Sham-PHE group. The treatment with PHE enhances the endothelium-dependent coronary relaxation and improves cardiovascular parameters, which suggests a therapeutic role of PHE.

Effects of chronic swimming training and oestrogen therapy on coronary vascular reactivity and expression of antioxidant enzymes in ovariectomized rats.

The aim of this study was to evaluate the effects of swimming training (SW) and oestrogen replacement therapy (ERT) on coronary vascular reactivity and the expression of antioxidant enzymes in ovariectomized rats. Animals were randomly assigned to one of five groups: sham (SH), ovariectomized (OVX), ovariectomized with E2 (OE2), ovariectomized with exercise (OSW), and ovariectomized with E2 plus exercise (OE2+SW). The SW protocol (5×/week, 60 min/day) and/or ERT were conducted for 8 weeks; the vasodilator response to bradykinin was analysed (Langendorff Method), and the expression of antioxidant enzymes (SOD-1 and 2, catalase) and eNOS and iNOS were evaluated by Western blotting. SW and ERT improved the vasodilator response to the highest dose of bradykinin (1000 ng). However, in the OSW group, this response was improved at 100, 300 and 1000 ng when compared to OVX (p<0,05). The SOD-1 expression was increased in all treated/trained groups compared to the OVX group (p<0,05), and catalase expression increased in the OSW group only. In the trained group, eNOS increased vs. OE2, and iNOS decreased vs. SHAM (p<0,05). SW may represent an alternative to ERT by improving coronary vasodilation, most likely by increasing antioxidant enzyme and eNOS expression and augmenting NO bioavailability.

Role of estrogen and progesterone in the modulation of CNG-A1 and Na/K+-ATPase expression in the renal cortex.

The steroid hormones, estrogen and progesterone, are involved mainly in the control of female reproductive functions. Among other effects, estrogen and progesterone can modulate Na(+) reabsorption along the nephron altering the body's hydroelectrolyte balance. In this work, we analyzed the expression of cyclic nucleotide-gated channel A1 (CNG-A1) and α1 Na(+)/K(+)-ATPase subunit in the renal cortex and medulla of female ovariectomized rats and female ovariectomized rats subjected to 10 days of 17ß-estradiol benzoate (2.0 µg/kg body weight) and progesterone (1.7 mg/kg body weight) replacement. Na(+)/K(+) ATPase activity was also measured. Immunofluorescence localization of CNG-A1 in the cortex and medulla was performed in control animals. We observed that CNG-A1 is localized at the basolateral membrane of proximal and distal tubules. Female ovariectomized rats showed low expression of CNG-A1 and low expression and activity of Na(+)/K(+) ATPase in the renal cortex. When female ovariectomized rats were subjected to 17ß-estradiol benzoate replacement, normalization of CNG-A1 expression and Na(+)/K(+) ATPase expression and activity was observed. The replacement of progesterone was not able to recover CNG-A1 expression and Na(+)/K(+) ATPase expression at the control level. Only the activity of Na(+)/K(+) ATPase was able to be recovered at control levels in animals subjected to progesterone replacement. No changes in expression and activity were observed in the renal medulla. The expression of CNG-A1 is higher in cortex compared to medulla. In this work, we observed that estrogen and progesterone act in renal tissues modulating CNG-A1 and Na(+)/K(+) ATPase and these effects could be important in Na(+) and water balance.

Influence of gender and estrous cycle on plasma and renal catecholamine levels in rats.

Several studies have demonstrated that gonadal hormones show significant effects on the brain and signaling pathways of effector organs/cells that respond to neurotransmitters. Since little information is available concerning the impact of male and female gonadal hormones on the renal and peripheral sympathetic system, the objective of this study was to further assess whether and how the renal content and plasma concentration of catecholamines are influenced by gender and the estrous cycle in rats. To achieve this, males Wistar rats were divided into 4 groups: (i) sham (i.e., control), (ii) gonadectomized, (iii) gonadectomized and nandrolone decanoate replacement at physiological levels or (iv) gonadectomized and nandrolone decanoate replacement at high levels. Female Wistar rats were divided into 6 groups: (i) ovariectomized (OVX), (ii) estrogen replacement at physiological levels and (iii) estrogen replacement at at high levels, (iv) progesterone replacement at physiological levels and (v) progesterone replacement at at high levels, and (vi) sham. The sham group was subdivided into four subgroups: (i) proestrus, (ii) estrus, (iii) metaestrus, and (iv) diestrus. Ten days after surgery, the animals were sacrificed and their plasma and renal catecholamine levels measured for intergroup comparisons. Gonadectomy led to an increase in the plasma catecholamine concentration in females, as well as in the renal catecholamine content of both male and female rats. Gonadectomized males also showed a lower level of plasma catecholamine than the controls. The urinary flow, and the fractional excretion of sodium and chloride were significantly increased in gonadectomized males and in the OVX group when compared with their respective sham groups.

Involvement of the atrial natriuretic peptide in the reduction of arterial pressure induced by swimming but not by running training in hypertensive rats.

The aim of this study was to compare, under resting conditions, the influence of chronic training in swimming or running on mean arterial pressure (MAP) and the involvement of the natriuretic peptide system in this response. Two-month-old male spontaneously hypertensive rats (SHR) were divided into three groups-sedentary (SD), swimming (SW) and running (RN)-and were trained for eight weeks under regimens of similar intensities. Atria tissue and plasma atrial natriuretic peptide (ANP) concentrations were measured by radioimmunoassay. ANP mRNA levels in the right and left atria as well as the natriuretic peptide receptors (NPR), NPR-A and NPR-C, mRNA levels in the kidney were determined by real-time PCR. Autoradiography was used to quantify NPR-A and NPR-C in mesenteric adipose tissue. Both training modalities, swimming and running, reduced the mean arterial pressure (MAP) of SHR. Swimming, but not running, training increased plasma levels of ANP compared to the sedentary group (P<0.05). Expression of ANP mRNA in the left atrium was reduced in the RN compared to the SD group (P<0.05). Expression of NPR-A and NPR-C in the kidneys of the SW group decreased significantly (P<0.05) compared to the SD group. Although swimming increased (125)I-ANP binding to mesenteric adipose tissue, displacement by c-ANF was reduced, indicating a reduction of NPR-C. These results suggest that the MAP reduction induced by exercise in SHR differs in its mechanisms between the training modalities, as evidenced by the finding that increased levels of ANP were only observed after the swimming regimen.

Acute obstructive apnea produces natriuresis in spontaneously hypertensive rats (SHR) by a renal nerve-dependent.

The role of renal nerve in excretion was investigated during acute obstructive apnea (OA) episodes in SHR. The animals (SHR and control, C) were presented for renal denervation (D; CD; SHRD) or undenervation (U; CU; SHRU). Tracheal catheterization was performed to induce OA via its total occlusion. Urine samples were collected every 2 min after 20 s of OA. Obstructive apnea resulted in bradycardia, hypotension, and induced elevations in the urinary measurements in SHRU, but not in CU. Conversely, the denervation increased in CD, but not in the SHRD. Urinary excretion was dependent of renal nerve in SHR during OA.

Cardiovascular effects of scorpionfish (Scorpaena plumieri) venom.

The aim of the present study was to investigate the cardiovascular activity of Scorpaena plumieri venom in both in vivo and in vitro models. In anesthetized rats, doses of the venom (14-216 microg protein/kg) induced a transient increase in the mean arterial pressure. However at higher dose (338 microg protein/kg) this effect was followed by a sudden hypotension and the animal evolved to death. The heart rate was temporarily increased and followed by bradycardia using doses > or =108 microg/kg. In isolated rat hearts the crude venom (5-80 microg protein) produced dose-dependent positive ventricular chronotropic, inotropic, lusitropic and coronary vasoconstriction responses. Partial purification of an active fraction (CF, cardiovascular fraction) which reproduced the cardiovascular effects induced by crude venom on isolated hearts was achieved by conventional gel filtration chromatography. Adrenergic blockades, prazosin and propranolol, significantly attenuated these responses. The coronary vasoconstriction response to CF was also attenuated by chemical endothelium denudation. In conclusion, the data showed that S. plumieri fish venom induces disorders in the cardiovascular system. It also suggests that alpha(1) and beta-adrenergic receptors, and the vascular endothelium, are involved at least partially, in these cardiac effects.

Role of cardiac hypertrophy in reducing the sensitivity of cardiopulmonary reflex control of renal sympathetic nerve activity in spontaneously hypertensive rats.

The gain of the volume-sensitive cardiopulmonary reflex (VSCR) is impaired in spontaneously hypertensive rats (SHR). Sensitivity of VSCR control of efferent renal sympathetic nerve activity (RSNA) in SHR is restored when cardiac hypertrophy and hypertension are reduced by enalapril treatment. The present study investigated which of these two parameters, cardiac hypertrophy or hypertension, has more influence on the impairment of VSCR control of RSNA in SHR. Rats (SHR or Wistar-Kyoto (WKY) rats) were treated with enalapril (10 mg/kg per day; SHRE and WKYE groups, respectively) or hydralazine (5 mg/kg per day; SHRH and WKYH groups, respectively) mixed in their food for 1 month. Control SHR and WKY rats were fed a normal diet. After the treatment regimen, the VSCR was evaluated by determining the decrease in RSNA elicited by acute isotonic saline volume expansion. Mean arterial pressure (MAP) was assessed via an intrafemural catheter and cardiac hypertrophy was determined by the left ventricular (LV) weight/bodyweight (BW) ratio. Afferent baroceptor nerve activity (BNA) was also evaluated during volume expansion to verify participation of the baroreflex. Volume expansion produced an attenuated renal sympathoinhibitory response in SHR compared with WKY rats. Enalapril treatment restored the volume expansion-induced decrease in RSNA in SHRE (-41 +/- 8%) compared with WKY rats (-44 +/- 3%). Although both enalapril and hydralazine treatment reduced MAP in SHR (P < 0.01; 126 +/- 5, 133 +/- 6 and 160 +/- 6 mmHg in SHRE, SHRH and SHR, respectively), hydralazine did not restore the sensitivity of VSCR control of RSNA in SHRH. Spontaneously hypertensive rats with established hypertension had a higher LV/BW ratio compared with WKY rats (3.22 +/- 0.14 vs 1.98 +/- 0.06 mg/g, respectively; P < 0.01). Enalapril reduced the LV/BW ratio in SHRE (2.30 +/- 0.07 mg/g; P < 0.01). Although hydralazine reduced LV hypertrophy, there was a weaker reduction in SHRH (2.68 +/- 0.04 mg/g; P < 0.05) compared with SHRE. There was no statistically significant difference among the WKY rat, WKYE and WKYH groups (P > 0.05). There was no change in afferent BNA during volume expansion in normal or hypertensive animals. Taken together, these results indicate that the impairment of VSCR control of RSNA in the SHR model of hypertension correlates better with the magnitude of cardiac hypertrophy than the level of arterial pressure.

Higher physiological doses of nandrolone decanoate do not influence the Bezold-Jarish reflex control of bradycardia.

BACKGROUND: We investigated the influence of short-term treatment with supraphysiological doses of an anabolic-androgenic steroid on the Bezold-Jarisch reflex (BJR) control of heart rate (HR) and whether this treatment induced cardiac hypertrophy and anabolic effects in rats. METHODS: Male rats were treated with nandrolone decanoate (10 mg/kg(-1) body weight/4 weeks; DECA) or vehicle control (CON). After 4 weeks of treatment, BJR was evaluated by bradycardia responses that were elicited by serotonin administration (2-32 microg/kg(-1)). Mean arterial pressure (MAP) was assessed and cardiac hypertrophy was determined by the left ventricle weight/body weight (LVW/BW) ratio. Histological analyses of LV and the measurement of the total body protein content of the animals were performed. RESULTS: Nandrolone decanoate (ND) treatment had no effect on the MAP (CON=105+/-5; DECA=110+/-3 mmHg). However, the mean basal HR of DECA animals was significantly lower than that of control animals (CON = 381+/-14; DECA=324+/-12 bpm; p<0.01). ND did not change the sensitivity of the BJR. The LVW/BW ratio indicated significant hypertrophy of the LV in DECA animals (CON=1.76+/-0.04; DECA=2.0+/-0.04 mg/g; p<0.01). Histological and morphometrical analyses demonstrate that there is also modest myocyte hypertrophy (CON=14.5+/-1.5; DECA=20.0 +/- 0.9 myocyte nuclei/field; p<0.05). However, the Masson-trichromic-stained samples showed an enhancement of collagen deposits on the LV matrix. CONCLUSIONS: We concluded that 4 weeks ND treatment induced an anabolic effect and the beginnings of LV remodeling, mainly due to excessive collagen deposition in the cardiac extracellular matrix. However, the treatment did not influence BJR control of bradycardia, an effect that could be explained by an enhanced efferent vagal tonus in DECA animals.

Activity of angiotensin-converting enzyme after treatment with L-arginine in renovascular hypertension.

The renin-angiotensin system plays a role in the pathophysiology of renovascular hypertension. In addition, some studies have demonstrated a beneficial effect of L-arginine (L-Arg), the precursor of nitric oxide (NO), in this model of hypertension. This study was designed to investigate the effects of L-Arg on cardiovascular parameters and on the activity of the angiotensin-converting enzyme (ACE), after 14 days of renovascular hypertension. The experiments were performed on conscious male Wistar rats. Two-kidney, one-clip renovascular hypertension (2KIC) was initiated in rats by clipping the left renal artery during 14 days, while control rats were sham-operated. One group was submitted to a similar procedure and treated with L-Arg (10 mg/ml; average intake of 300mg/day) from the 7th to the 14th day after surgery, whereas the respective control group received water instead. At the end of the treatment period, the mean arterial pressure (MAP) was measured in conscious animals. The rats were sacrificed and the ACE activity was assayed in heart and kidneys, using Hip-His-Leu as substrate. In a separate group, the heart was removed, the left ventricle (LV) was weighed and the LV/body weight ratios (LV/BW) were determined. We observed significant differences in MAP between the L-Arg-treated and untreated groups (129 +/- 7 vs. 168 +/- 6 mmHg; P< 0.01). The cardiac hypertrophy described for this model of hypertension was attenuated in the 2K1C-L-Arg-treated group (14th day, wet LV/BW: 2K1C-L-Arg = 1.88 +/- 0.1; 2K1C = 2.20 +/- 0.1 mg/g; P < 0.05). L-Arg administration caused an important decrease in cardiac ACE activity (2K1C-L-Arg: 118 +/- 15; 2K1C: 266 +/- 34 micromol/min/mg; P < 0.01). L-Arg also decreased the ACE activity in the clipped kidney by 47% (P < 0.01), but not in the nonclipped kidney. These data suggest that increased NO formation and reduced angiotensin II formation are involved in the anthihypertensive effect of orally administered L-arginine.