Differential effects of progesterone and 17 beta-estradiol on the Ca2+ entry induced by thapsigargin and endothelin-1 in in situ endothelial cells

The effects of progesterone and 17 beta -estradiol on Ca2+ signaling in in situ endothelial cells were investigated using front-surface fluorometry of fura-2-loaded strips of porcine aortic valve. Progesterone inhibited the t hapsigargin-induced sustained [Ca2+](i) elevation (IC50 = 33.9 muM, n = 4), while 17 beta -estradiol added a transient [Ca2+](i) elevation. Progestero ne and 17 beta -estradiol had no significant effect on the thapsigargin-ind uced [Ca2+](i) elevations in the absence of extracellular Ca2+. A Mn2+-indu ced decline of fluorescent intensity at 360 nm excitation was accelerated b y thapsigargin. This acceleration was completely reversed by progesterone, but not by 17 beta -estradiol. Progesterone inhibited, and 17 beta -estradi ol enhanced the endothelin-1 (ET-1)-induced [Ca2+](i) elevation, while both had no effect on the ET-1-induced Ca2+ release observed in the absence of extracellular Ca2+ or in the pertussis toxin-treated strips. Progesterone a nd 17 beta -estradiol thus had different effects on Ca2+ signaling, especia lly on Ca2+ influx, in endothelial cells. (C) 2000 Elsevier Science B.V. Al l rights reserved.