Journal
METHODS AND FINDINGS IN EXPERIMENTAL AND CLINICAL PHARMACOLOGY
Volume 25, Issue 10, Pages 817-822Publisher
PROUS SCIENCE, SA
DOI: 10.1358/mf.2003.25.10.793331
Keywords
alpha(2)-adrenoceptors; endothelin; nitric oxide; Pausinystalia yohimbie; renal medullary blood flow; vasoconstriction; Yohimbine
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The bark of the African tree Pausinystalia yohimbe has been used as a food additive with aphrodisiac and penile erection enhancing properties. The effect of an aqueous extract of P. yohimbe (CCD-X) on renal circulation was assessed in order to test the hypothesis that it possesses additional effects on nitric oxide production and/or endothelin-1 (ET-1)-like actions. In vivo studies with CCD-X in Sprague Dawley rats demonstrated a dose-dependent (1-1000 ng/kg) increase in mean blood pressure (p < 0.001) and an increase in medullary blood flow (MBF) (p < 0.001). Both the pressor action and renal medullary vasodilation were blocked by endothelin(A) (ETA) receptor antagonist BMS182874 and endothelm(B) (ETB) receptor antagonist BQ788 in combination. L-N-w-nitro-l-arginine methyl ester (L-NAME; 10 mg/kg) also inhibited the increase in MBF induced by CCD-X. In vitro studies in isolated perfused kidney and in pressurized renal microvessels confirmed the dose-dependent vasoconstrictor action of this extract. ETA receptor antagonist BQ610 and ET, receptor antagonist BQ788 separately and significantly attenuated the renal vasoconstrictor actions of the extract (p < 0.001 ANOVA). These preliminary observations indicate that, in addition to the a-adrenergic antagonist actions that characterize yohimbine, CCD-X possesses endothelin-like actions and affects nitric oxide (NO) production in renal circulation. These findings suggest a strong possibility of post-receptor cross-talk between alpha(2)-adrenoceptors and endothelin, as well as a direct affect of alpha(2)-adrenoceptors on renal NO production. (C) 2003 Prous Science. All rights reserved.
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