Abstract

The effects of an inhibitor of ADP/ATP translocase (AAT) mainly expressed in the mitochondria inner membrane, atractyloside (ATR), on the gating property of the Ca2+channels in the sarcoplasmic reticulum (SR) vesicles from the rabbit skeletal muscle were investigated using ion flux measurement and single channel recording. At 10 μM of cytoplasmic Ca2+, ATR decreased the rate constant of choline+influx through the Ca2+channels up to about 60% and perfectly inhibited about half the population of single Ca2+channels incorporated into planar bilayers. Furthermore, the inhibition of the Ca2+channels by ATR was effective at lower Ca2+. These results support the previous results that AAT exists in the skeletal muscle SR and plays a key role in the Ca2+mobilization of the skeletal muscle cell [Yamaguchi, N., and Kasai, M. (1998)Biochem. J.335, 541–547], and the number of Ca2+channels regulated by AAT is thought to depend on the cytoplasmic Ca2+concentration.

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