Isoproterenol and GTPγS inhibit L-type calcium channels of differentiating rat skeletal muscle cells

✍ Scribed by B. Somasundaram; R. T. Tregear

• Publisher: Springer Netherlands
• Year: 1993
• Tongue: English
• Weight: 522 KB
• Volume: 14
• Category: Article
• ISSN: 0142-4319
• DOI: 10.1007/bf00123099

✦ Synopsis

In adult skeletal muscle, G-proteins have been shown to modulate the calcium channels both directly and through a cAMP-dependent phosphorylating mechanism. We have investigated the action of G-proteins on the L-type calcium current in cultured rat muscle cells (myoballs) under voltage clamp in whole cell or perforated patch modes. Intracellular photolytic release of 200 p.M GTP~S inhibited the L-type calcium current. Inclusion of 500 laM uncaged GTPrS in the patch pipette in the whole cell configuration reduced the calcium current by a similar amount. Under perforated patch conditions external application of 10 laM of the 13-adrenergic agonist isoproterenol also reduced the calcium current. Pretreatment of the cells with pertussis toxin reversed the effect of GTPrS and removed that of isoproterenol. We conclude that rat myoballs contain 13-adrenergic receptors that inhibit the L-type calcium current, and that this inhibition is mediated by a pertussis toxinsensitive G-protein.