Ca2+ Spark as a Regulator of Ion Channel Activity

The Japanese Journal of Pharmacology

Susumu Ohya²  Katsuhiko Muraki²  Minoru Watanabe²  Yuji Imaizumi¹  Hisao Yamamura¹  Yoshiaki Ohi¹ 

[1] Department of Pharmacology & Therapeutics, Faculty of Pharmaceutical Sciences, Nagoya City University;Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University

关键词: Calcium spark;    Ryanodine receptor;    Cardiac muscle;    Smooth muscle;    Potassium channel;   

DOI  :  10.1254/jjp.80.1

学科分类：药理学

来源: Nihon Yakuri Gakkai Henshuubu / Japanese Pharmacological Society

【 摘 要 】

References(42)Cited-By(27)Ca2+ spark is a local and transient Ca2+ release from sarcoplasmic reticulum (SR) through the ryanodine receptor Ca2+-releasing channel (RyR). In cardiac myocytes, Ca2+ spark is an elementary unit of Ca2+-induced Ca2+ release (CICR) by opening of RyR(s) in junctional SR (jSR), which is triggered by Ca2+-influx through L-type Ca2+ channels to the narrow space between a transverse tubule and jSR. Ca2+ spark has, therefore, been described as the evidence for “the local control of excitation-contraction coupling”. In contrast, Ca2+ sparks in smooth muscle have been reported in relation to Ca2+-dependent K+ (KCa) channel activation and muscle relaxation. A spontaneous Ca2+ spark in a superficial area activates 10 - 100 KCa channels nearby and induces membrane hyperpolarization, which reduces Ca2+ channel activity. In several types of smooth muscle cells, which have relatively high membrane excitability, an action potential (AP) elicits 5 - 20 Ca2+ hot spots (evoked sparks with long life) in the early stage via CICR in discrete superficial SR elements and activates KCa-channel current highly responsible for AP repolarization and afterhyperpolarization. CICR available for contraction may occur more slowly by the propagation of CICR from superficial SR to deeper ones. The regulatory mechanism of ion channel activity on plasma membrane by superficial SR via Ca2+ spark generation in smooth muscle cells may be analogously common in several types of cells including neurons.

【 授权许可】

Unknown