PAF activation of a voltage‐gated R‐type Ca2+ channel in human and canine aortic endothelial cells

By the use of fura‐2 and digital imaging techniques, [K]o depolarization or PAF (10−9 m) were shown to induce a sustained increase of [Ca]i in human or canine single aortic vascular endothelial cells (VEC) that was insensitive to nifedipine but sensitive to (−)‐PN200–110 or to lowering of [Ca]o. The PAF‐induced effect on [Ca]i was blocked by the PAF receptor antagonist, WEB2170. Our results suggest that [K]o depolarization and PAF increase [Ca]i via the activation of R‐type Ca2+ channels.