cGMP stimulates endoplasmic reticulum Ca(2+)-ATPase in vascular endothelial cells

Calcium is a crucial regulator of many physiological processes such as cell growth, division, differentiation, cell death and apoptosis. In this study, we examined the effect of cGMP on agonist-induced Ca(2+)](i) transient in isolated rat aortic endothelial cells. 100 microM ATP was applied to the cells bathed in a Ca(2+)-free physiological solution to induce a Ca(2+)](i) transient that was caused by Ca(2+) release from intracellular stores. cGMP, which was applied after Ca(2+)](i) reached its peak level, accelerated the falling phase of Ca(2+)](i) transient. Pre-treatment of the cells with CPA abolished the accelerating effect of cGMP on the falling phase of Ca(2+)](i) transient. The effect of cGMP was reversed by KT5823, a highly specific inhibitor of protein kinase G. Taken together, these data suggest that cGMP may reduce Ca(2+)](i) level by promoting Ca(2+) uptake through sarcoplasmic/endoplasmic reticulum ATPase and that the effect of cGMP may be mediated by protein kinase G.