Release of prostacyclin and EDRF from endothelial cells is differentially controlled by extra- and intracellular calcium.
The aim of this study was to define the roles of extra- and intracellular Ca++ in the release of PGI2 and EDRF from cultured bovine endothelial cells stimulated with receptor-mediated and receptor-independent substances. The receptor-mediated stimulant bradykinin (10 nM) elicited transient releases of PGI2 (assayed with radioimmunoassay of 6-keto PGF1 alpha) and EDRF (assayed by its stimulatory effect on purified soluble guanylate cyclase). Bradykinin also elicited dose-dependent increases in intracellular free calcium [( Cai++], measured with the fluorescent probe indo-1). In the absence of extracellular Ca++ (nominally Ca+(+)-free, EGTA 0.1 mM) or in the presence of the intracellular calcium antagonist TMB-8 (0.1 mM), PGI2 release was significantly attenuated. Bradykinin-induced EDRF release was not significantly affected by TMB-8 but was completely abolished in Ca+(+)-free medium. When endothelial cells were stimulated with thimerosal (an inhibitor of the enzyme acyl-CoA-lysolecithin-acyl-transferase; 5 microM), a long-lasting release of EDRF and PGI2 was induced, associated with only a slight increase in [Cai++]. Removal of extracellular Ca++ had little effect on [Cai++], completely abolished EDRF release, and did not change PGI2 release. It is concluded that there is a close association between PGI2 release and [Cai++] in bradykinin-stimulated endothelial cells. In contrast to PGI2 synthesis, EDRF production is directly dependent on extracellular Ca++ and independent of [Cai++].
Lückhoff
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Institute of Applied Physiology, University of Freiburg, Federal Republic of Germany.
D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D011464:Epoprostenol / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*
D009569:Nitric Oxide; D011464:Epoprostenol; D002118:Calcium