Signal transduction and Ca2+ uptake activated by endothelins in rat brain endothelial cells

The activation of signal transduction pathways by endothelin-1 or endothelin-3 were investigated in rat cerebromicrovascular endothelial cells. Endothelin-1 induced a rapid increase in inositol triphosphate (IP3) formation in these cells, whereas endothelin-3 was only moderately effective at high concentrations. Both endothelins also increased uptake of 45Ca2+ in these cells. Endothelin-1-induced IP3 formation or 45Ca2+ uptake were inhibited by endothelin ETA receptor antagonist BQ-123. Ryanodine, an inhibitor of intracellular Ca2+ mobilization, selectively endothelin-1-induced 45Ca2+ uptake, whereas nickel or suramin inhibited endothelin-3-induced 45Ca2+ uptake. The results indicate that endothelin-1 elevates 45Ca2+ uptake in rat brain endothelial cells by mechanisms coupled to the mobilization of intracellular Ca2+ stores. Both endothelin-1- and endothelin-3-induced 45Ca2+ uptake were inhibited by receptor operated Ca2+ channel blocker SK&F 96365, whereas they were insensitive to dihydropyridine derivatives nifedipine and nitrendipine. The release of arachidonic acid from rat brain endothelial cells observed in response to endothelin-1 was inhibited by ryanodine or SK&F 96365, implicating participation of both intra- and extra- cellular components of Ca2+ signaling in activating endothelial secretion of vasoactive substances.