Gender difference in the basal intracellular Ca2+ concentration in rat valvular endothelial cells

Intracellular Ca2+ concentration ([Ca2+](i)) was measured by Fura 2/AM fluorescence imaging microscopy in freshly isolated valvular endothelial cells taken from female and male rats. The basal level of [Ca2+](i) was significantly elevated in female valvular endothelial cells when compared to males (P < 0.05). Inhibition of the sarco-endoplasmic reticulum Ca2+-ATPase with cyclopiazonic acid (CPA, 10 mu M) caused a greater increase in the [Ca2+](i) in female than male endothelial cells. Removal of extracellular Ca2+ returned the [Ca2+](i) to the basal level. The rate of [Ca2+](i) decline was significantly slower in female endothelial cells compared to males. There were no differences in the unstimulated rate of Mn2+ quenching between two groups. These results demonstrate that estrogen affects NOS at least in part, by an alteration in Ca2+ homeostasis in endothelial cells. (C) 1998 Academic Press.