Ca-independent contraction of porcine coronary artery induced by endothelin

• Published in: Japanese Journal of Pharmacology Vol. 49; no. suppl; p. 105
• Main Authors: Kodama, Mayuko, Abe, Shimako, Kanaide, Hideo
• Format: Journal Article
• Language: English
• Published: The Japanese Pharmacological Society 1989
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1016/S0021-5198(19)56159-5

Using front-surface fluorometry and porcine coronary arterial strips loaded with fura-2, effects of endothelin (ET) on cytosolic Ca concentrations, [Ca]i, and tension development were investigated. In the presence of 1.25 mM extracellular Ca, ET induced a rapid and sustained increase in [Ca]i and contraction, in a dose-dependent manner. When 10-7 M ET was applied, peak levels of fluorescence and tension were about 90% and 160% , respectively, of the levels observed with strips in 118 mM K solution. In the absence of extracellular Ca, ET induced a transient increase in [Ca]i and contraction. The increases in fluorescence and tension induced by 10-7 M ET were 59% and 71% of the levels observed in the presence of extracellular Ca, respectively. When caffeine-sensitive intracellular Ca stores were depleted by repeated applications of 20 mM caffeine in the absence of extracellular Ca, ET induced a transient contraction, with no increase in [Ca]i. The extent of the contraction induced by 10-7 M ET was 23% of the level observed in the presence of extracellular Ca. Thus, it is suggested that in addition to extracellular Ca-dependent events, ET induces an increase in [Ca]i by releasing Ca from intracellular stores, and contraction. In vascular smooth muscle, ET apparently a Ca-independent contraction.