Effects of ryanodine on acetylcholine-induced Ca mobilization in single smooth muscle cells of the porcine coronary artery.

Autor: Katsuyama, Hideaki, Ito, Shinichi, Itoh, Take, Kuriyama, Hirosi
Zdroj: Pflügers Archiv: European Journal of Physiology; 1991, Vol. 419 Issue 5, p460-466, 7p
Abstrakt: To study the essential features of acetylcholine (ACh)-and caffeine-sensitive cellular Ca storage sites in single vascular smooth muscle cells of the porcine coronary artery, the effects of ryanodine on both ACh- and caffeine-induced Ca mobilization were investigated by measuring intracellular Ca concentration ([Ca]) using Fura 2 in Ca-containing or Ca-free solution. The resting [Ca] of the cells was 122 nM in normal physiological solution and no spontaneous activity was observed. In a solution containing 2.6 mM Ca, 10 μM ACh or 128 mM K produced a phasic, followed by a tonic, increase in [Ca] but 20 mM caffeine produced only a phasic increase. In Ca-free solution containing 0.5 mM ethylenebis(oxonitrilo)tetraacetate (EGTA), the resting [Ca] rapidly decreased to 102 nM within 5 min, and 10 μM ACh or 20 mM caffeine (but not 128 mM K) transiently increased [Ca]. Ryanodine (50 μM) greatly inhibited the phasic increase in [Ca] induced by 10 μM ACh or 5 mM caffeine and increased the time to peak and to the half decay after the peak in the presence or absence of extracellular Ca. By contrast, ryanodine (50 μM) enhanced the tonic increase in [Ca] induced by 128 mM K and also by 10 μM ACh in Ca-containing solution. In Ca-free solution containing 0.5 mM EGTA, ACh (10 μM) failed to increase [Ca] following application of 20 mM caffeine. The level of [Ca] induced by 20 mM caffeine was greatly reduced, but not abolished, following application of 10 μM ACh in Ca-free solution. These results suggest that both ACh and caffeine release Ca from the ryanodine-sensitive sarcoplasmic reticulum (SR) in smooth muscle cells of the porcine coronary artery. The finding that ryanodine significantly increased the resting [Ca] and inhibited the rate of decline of [Ca] following wasthout of high K or ACh in Ca-containing solution suggests that SR may negatively regulate the resting [Ca] in smooth muscle cells of the porcine coronary artery. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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