The Possible Regulatory Mechanisms of Aqueous, Ethyl Acetate and NHexane Fractions of the Ribes khorassanicum Extract on Acute Hypertension in Rats.

OBJECTIVE: Our previous studies showed the antihypertensive effect of Ribes khorassanicum (R. khorassanicum), a medicinal herb growing in the North Khorasan Province of Iran. For further evaluation, the present study investigated the effect of n-hexane (HX), ethyl acetate (EA), and aqueous (AQ) fractions of hydroalcoholic R. khorassanicum extract on cardiovascular responses in angiotensin II (AngII) and NG-nitro-L-arginine methyl ester (L-NAME) hypertensive rats. METHODS: Wistar rats were randomly divided into 11 groups (n=5): 1) control, 2) AngII (50 ng/kg, i.v), 3) AngII + losartan (Los, 10 mg/kg, i.p), 4) L-NAME (10 mg/kg, i.v), 5) L-NAME+ sodium nitroprusside (SNP) (50 mg/kg, i.p), 6, 7, 8) one dose of each fraction of R. khorassanicum (AQ/EA/HX (50 mg/kg, i.p)) +AngII, Los 9, 10, 11) one dose of each fraction of R. khorassanicum (AQ/EA/HX (50 mg/kg, i.p)) + L-NAME. Treated rats received three fractions 30 min before the injection of L-NAME and AngII in separate groups. The cardiovascular parameters were recorded by the Power Lab instrument via an angiocath inserted into the femoral artery. The peak changes (Δ) of Mean Arterial Pressure (MAP), Systolic Blood Pressure (SBP), and Heart Rate (HR) in treated groups were compared with those of the hypertensive and control groups. RESULT: AngII and L-NAME significantly increased ΔMAP and ΔSBP and attenuated by pretreatment of Los and SNP, respectively. Pretreatment with polar (AQ) and semipolar (EA) fractions of R. khorassanicum reduced the peak changes of MAP and SBP in both AngII and L-NAME-treated groups. Only the fraction of the herb attenuated the HR increased in the L-NAME group. The HR in other groups did not demonstrate any significant difference. CONCLUSION: All fractions of R. khorassanicum have an antihypertensive effect. However, the effect of polar fractions is more salient. It is also conceivable that the antihypertensive effect of fractions is mostly mediated by the inhibition of AngII.

Ethyl Acetate and Aqueous Fractions of Ziziphus jujuba Prevent Acute Hypertension Induced by Angiotensin II in Rats.

BACKGROUND: The effect of hydroalcoholic extract of Ziziphus jujuba (ZJ) on hypertension has been reported previously. OBJECTIVE: This experiment investigates the effect of two ethyl acetate (EA, a polar and semi-polar compound) and aqueous fractions (AQ, a polar compound) of ZJ extract on cardiovascular parameters in acute hypertension induced by angiotensin II (AngII). METHODS: Rats were randomly divided into following groups (n=7 in each group): 1) Control; 2) AngII (50 ng/kg); 3) Losartan (LOS, 30 mg/kg) + AngII; 4, 5) ethyl acetate fraction (EA150 and EA300 mg/kg) + AngII and 6, 7) aqueous fraction (AQ150 and AQ300 mg/kg) + AngII. Rats were treated with both fractions and LOS orally for four weeks and in the experiment day (28th) AngII intravenously injected and cardiovascular parameters (Systolic Blood Pressure (SBP), Mean Arterial Pressure (MAP) and Heart Rate (HR)) directly were recorded by a power lab system. RESULTS: AngII could significantly increase SBP and MAP (P<0.001) and decrease HR with respect to the control and these responses were attenuated by LOS. The SBP and MAP in both doses of EA+ AngII and the higher dose of AQ fractions + AngII were significantly lower than the AngII group (P<0.05 to P<0.001). Bradycardia induced by AngII was also reduced by LOS and both fractions. The comparison of two fractions also showed that the effect of EA fraction is greater than the AQ. CONCLUSION: This study indicates that both fractions of the ZJ extract have a beneficial effect on hypertension. Because effect of EA was greater than AQ, we suggested that antihypertensive effects of ZJ mediated polar and nonpolar compounds.

Involvement of ß-adrenergic receptor of nucleus tractus solitarius in changing of baroreflex sensitivity by estrogen in female rats.

BACKGROUND: Arterial baroreflex (ABR) is an important factor in preventing of blood pressure fluctuations that determined by baroreflex sensitivity (BRS). Estrogen is an ovarian hormone that has influence on ABR. The mechanism of this effect of estrogen unknown and may be mediated by ß-adrenergic receptor of nucleus tractus solitarius (NTS), an important area in regulation of baroreflex. Therefore, in this study changing of BRS by estrogen after blockade ß-adrenergic receptor of NTS in ovariectomized rats (Ovx) and Ovx treated with estrogen (Est) was examined. MATERIALS AND METHODS: After ovariectomy, all female rats divided to Ovx and Ovx + Est groups and two series of experiments were performed. In the first experiment, phenylephrine was [intravenously, IV] injected in both the Ovx and Ovx + Est groups, and mean arterial pressure (MAP), heart rate (HR), and BRS were evaluated (n = 8 for each group). In the second experiment, each of Ovx and Ovx + Est groups divided into saline and propranolol (pro) groups, saline and pro stereotaxically were microinjected into NTS, respectively. Further, phenylephrine (IV) was injected in all groups and BRS was evaluated. RESULTS: BRS significantly increased in estrogen-treated groups (Ovx + Est) compared to Ovx groups (P < 0.01). The blockade ß-adrenergic receptor of NTS by pro did not significantly changed BRS in both Ovx and Ovx + Est groups. CONCLUSION: We concluded that there aren't any intraction between estrogen and ß-adrenergic receptor of NTS in BRS.