CA-2+-DEPENDENT INHIBITION OF CA-2+-INDEPENDENT CONTRACTION IN UTERINE SMOOTH-MUSCLE

被引:6
作者
ISHINE, T [1 ]
MIYAUCHI, Y [1 ]
GOKITA, T [1 ]
MATSUO, K [1 ]
UCHIDA, MK [1 ]
机构
[1] MEIJI COLL PHARM,DEPT MOLEC PHARMACOL,1-35-23 NOZAWA,SETAGAYA KU,TOKYO 154,JAPAN
关键词
CA-2+; SMOOTH MUSCLE; RELAXATION; UTERUS;
D O I
10.1016/0014-2999(92)90307-P
中图分类号
R9 [药学];
学科分类号
1007 ;
摘要
Uterine smooth muscle of the rat shows Ca2+-independent contraction in response to oxytocin in Ca2+-free medium. Micromolar Ca2+ inhibits this contraction. We now tested whether Ca2+ itself is the cause of this inhibition. The ratio of fura-2 fluorescence, the indicator of the intracellular level of Ca2+, was increased in parallel with the degree of inhibition by Ca2+. When inhibition was elicited by Ca2+, EGTA released the inhibition. Comparison of the dose-response curve for oxytocin in Ca2+-free solution and that in the medium with 1-mu-M Ca2+ showed that the inhibition by Ca2+ is non-competitive. EGTA chelation of the intracellular Ca2+ by loading of EGTA as its acetoxymethylester resulted in diminution of inhibition by Ca2+. EGTA suppressed the Ca2+-induced contraction but did not affect Ca2+-independent contraction. It is concluded that the inhibition is induced by intracellular Ca2+ itself.
引用
收藏
页码:285 / 288
页数:4
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