Effect of glycerol treatment on the calcium current of frog skeletal muscle.

Abstract

Current and voltage clamp experiments were carried out on frog skeletal muscle fibers. For voltage clamp, the 3 micro-electrode technique near the fiber end was used. Ca spikes and currents were recorded in TEA [tetraethylammonium] sulfate saline. The addition of 400 mM-glycerol did not appreciably modify them. Muscle fibers were detubulated with the glycerol method. They showed Na propagating action potentials with Na and K currents of expected amplitudes. Ca spikes and currents were reduced or abolished in detubulated muscle fibers. An analysis of fiber capacitance showed a linear correlation between the remaining ICa [ionic strength of Ca] and the degree of electric discontinuity between the transverse tubular system and the surface membrane. Apparently ICa is mainly located in the transverse tubular system. This localization is compatible with some role during mechanical activation.