Effects of piperine on uterine blood flow

Abstract

Effects of piperine on uterine blood flow were investigated in anesthetized nonpregnant and pregnant rats by using ultrasonic pulse Doppler flowmeter. Intra-arterial injection of piperine (0.5-2.0 mg/kg) produced an initial fall and followed by a transient elevation of systemic blood pressure. Changes in arterial blood pressure resulted in a linear changes in uterine blood flow. The increase of blood pressure as well as uterine blood flow in both nonpregnant and pregnant rats showed a dose dependent to piperine. Piperine also produced a substantial decrease and followed by a marked increase of femoral blood flow. Meanwhile, common carotid blood flow was sustained fall. Mechanism of action of piperine was investigated. Concurrent to the elevation of blood pressure by piperine, the femoral blood flow and common carotid blood flow were reduced. The increase in peripheral resistance by vasoconstriction of these vessels was suggested to be responsible for the pressor effect of piperine. The pressor effect was attenuated by phentolamine and isoptin but was enhanced by propranolol, atropine and reserpine. Thus the activation of β-adrenergic receptors as well as increase influx of Ca(2+) into the vascular cell might attribute to the vasoconstriction caused by piperine whereas a blockade of a muscarinic and β-adrenergic vasodilation enhanced the vasoconstriction. The elevation of uterine blood flow by piperine could not be blocked by all pharmacologic aniagonists used. The results suggest that (1) the pressor effect of piperine was intimately related to an adrenergic mechanism and Ca(2+) influx. It might result from the activation on the release of catecholamines by piperine and from the sympathetic agonistic action of piperine itself as well as a directly stimulating the influx of Ca(2+) into the cells. (2) The vasodilating effect of piperine was related to the direct effect of piperine.