Hypertensive effects of oral administration of the aqueous extract of Solanum torvum fruits in l-NAME treated rats: Evidence from in vivo and in vitro studies

Ethnopharmacological relevance

Solanum torvum fruits are commonly used in Cameroonian traditional medicine for treatment of arterial hypertension. It has been previously shown that intravenous administration of aqueous extract from dried fruits (AEST) reduced blood pressure.

Aim

The present work evaluates acute toxicity and effects of oral administration of AEST in chronic arterial hypertension induced by l-NAME. Effects of AEST were also evaluated on isolated aorta.

Materials and methods

AEST (200 mg/kg/day, p.o.) was given solely or concomitantly with l-NAME (40 mg/kg/day, p.o.) for 30 consecutive days. Animal body weight, systolic blood pressure and heart rate were measured before stating the treatment and at the end of each week. Urinary volume and urinary sodium and potassium contents were quantified before and at days 1, 15 and 30 of the treatment. Aorta from treated animals was tested for their sensitivity to noradrenalin and carbachol. Aorta from normal untreated rats was used to evaluate the in vitro vascular effect of AEST.

Results

The results showed that AEST did induce neither mortality nor visible signs of toxicity. When given solely or in co-administration with l-NAME, AEST significantly reduced animal's body weight. It amplified the hypertensive and cardiac hypertrophy effect of l-NAME and did not affect these parameters in normotensive animals. AEST increased the sensitivity to noradrenalin in normotensive and significantly reduced it in hypertensive animals. AEST significantly increased urinary volume and sodium excretion in l-NAME treated animals while reducing the sodium excretion in normotensive. In vitro, AEST induced a potent partial endothelium-dependent contraction of aortic ring; contractions that were partially antagonized by prazosin and verapamil and were not relaxed by carbachol.

Conclusion

These results suggest that oral chronic administration of AEST induced potentiation of arterial hypertension and cardiac hypertrophy in l-NAME treated rats. These effects may result from a reduction in sensitivity to vasorelaxant agents and increase in hypersensitivity to contractile factors. AEST possess potent in vitro vasocontractile activity that may result from activation of both α₁-adrenergic pathway and calcium influx.