E. Cairrão, J. Carvas, A.J. Santos-Silva, E. Alvarez, *I. Verde

CICS – Centro de Investigação em Ciências da Saúde, Universidade da Beira Interior, 6201-001 Covilhã, Portugal

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.

Keywords: sex hormones, steroid non-genomic effects, L-type Ca²⁺ currents, patch-clamp, A7r5 cells.

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