ANTI-HYPERTENSIVE AND CARDIOVASCULAR EFFECTS OF TAPINANTHUS DODONEIFOLIUS (DC. DANSER) (LORANTHACEAE) IN RATS.

Abstract

The hypotensive and anti-hypertensive effects of aqueous extract from Tapinanthus dodoneifolius (AETD) were examined in rats. Intravenous administrations of the plant extract (AETD 10-4 to 310-1 µg/kg iv) caused transient, dose-dependent and significant (p<0.05) reductions in basal arterial pressure of anaesthetised normotensive rats. Further more AETD (310-1 µg/kg) completely abolished adrenalin or phenylephrine evoked-hypertension on rats. The cardiovascular effects were then investigated. AETD did not affect heart rate, but significantly enhanced heart contraction force and relaxation capacity. Cumulative additions of T dodoneifolius aqueous extract (AETD 0.001- 1mg/ml) to the bath fluid induced concentration-dependent relaxation of endothelium-containing normotensive Wistar rat isolated aortic rings pre-contracted with phenylephrine (10-6M). The vasorelaxant effect of AETD on endothelium-containing isolated aortic rings was annulled by removal of the functional endothelium. When Indomethacin failed to inhibit AETD vasodilatory activity, pretreatment of the endothelium-containing vessels with NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS) completely abolished this vasodilatory effect. The findings of this experimental animal study suggest that T. dodoneifolius aqueous extract possess anti-hypertensive properties; this effect of the plant extract is likely to be mediated, at least in part, through vasorelaxant effect, through nitric oxide synthase activation and subsequent nitric oxide release.