[Release of endothelium-derived relaxing factor (EDRF) from cultured vascular endothelial cells depends on extra- and intracellular Ca2+ concentrations].
The objective of this study was to elucidate the role of extracellular and intracellular Ca2+ in EDRF release from vascular endothelial cells. Cultured fetal bovine aortic endothelial cells were stimulated by adenosine triphosphate (ATP), calcium ionophore (A23187), bradykinin (BKN) and acetylcholine (ACh). The amount of EDRF released was determined on the basis of the relaxation of rabbit aortic ring and the cGMP content of cultured smooth muscle cells derived from fetal bovine aorta. Changes in intracellular Ca2+ concentration ([Ca2+]i) were measured by a photometric fluorescence microscopy using Fura-2. ATP and A23187 induced dose-dependent increases in both [Ca2+]i and EDRF release. BKN increased both [Ca2+]i and EDRF release upon initial exposure (10(-8) M), but there were no further changes at higher concentrations because of desensitization. ACh induced no significant changes in either [Ca2+]i or EDRF release. There was a statistically significant correlation between agonist-induced changes in [Ca2+]i and the amount of EDRF released (p < 0.01). Removal of extracellular Ca2+ eliminated the continuous elevation induced by agonists of both [Ca2+]i and the amount of EDRF. The agonist-induced EDRF release was inhibited by L-NMA (N omega-methyl L-arginine). The EDRF release reduced by L-NMA was restored by adding L-arginine. Thus, the EDRF released from endothelial cells is thought to be an L-arginine-derived nitric oxide (NO) or an NO-related substances. These findings suggest that [Ca2+]i is closely linked to the amount of EDRF released, and that extracellular Ca2+ is essential for EDRF release because its influx is involved in the continuous elevation of [Ca2+]i.
Korenaga
R
R
Department of Cardiovascular Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000032:analysis / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000032:analysis; D004730:Endothelium, Vascular / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*
D009569:Nitric Oxide; D000001:Calcimycin; D000255:Adenosine Triphosphate; D006152:Cyclic GMP; D000109:Acetylcholine; D001920:Bradykinin; D002118:Calcium