The passive calcium leak in cultured porcine aortic endothelial cells.

Unidirectional 45Ca fluxes were measured to characterize the calcium-leak pathway in cultured endothelial cells of pig aorta. Lanthanum, but not other calcium channel blockers such as verapamil and diltiazem, inhibited the passive 45Ca uptake. Passive uptake of 45Ca across the plasma membrane increased progressively as extracellular pH was raised from 5.2 to 9.2. SK&F 96365, a putative inhibitor of receptor-mediated Ca2+ entry, selectively blocked ATP-induced 45Ca uptake. The Ca2+ leak pathway may play an important role in endothelial cell Ca2+ homeostasis which controls the basal and stimulated release of endothelium-derived relaxing factors (i.e., EDRF, prostacyclin) in physiological or pathological situations.