17 Beta-Estradiol and progesterone inhibit L-type Ca2+ current of rat aorta smooth muscle cells

Abstract

Sex hormones like 17ß-estradiol (ßES) and progesterone have shown rapid non-genomic vasodilator effects, which could be involved in the protection of cardiovascular system. However, the precise mechanism by which this effect occurs has not been elucidated yet, even if Ca2+ influx inhibition seems to be implicated. The aim of this study was to study the influence of ßES and progesterone on the L-type Ca2+ current measured by whole cell voltage-clamp in A7r5 cells. Voltage-operated Ca2+ currents were elicited by square-step voltage pulses and pharmacologically characterized as L-type currents by (-)-Bay K8644 (BAY) and nifedipine. Both ßES and progesterone (1-100 µM), rapidly and reversibly inhibited, in a concentration dependent manner, either non-stimulated or BAY-stimulated Ca2+ currents registered in A7r5 cells. These results suggest that ßES and progesterone inhibit L-type voltage-operated Ca2+ channels through a non-genomic pathway. Consequently, these hormones inhibit the Ca2+ entry into smooth muscle cells from rat aorta, an effect that can contribute for the protection of the cardiovascular system.