Hypertonicity-induced inhibition of excitation-contraction coupling in Xenopus twitch fibers.

Mechanical responses such as twitch and tetanus were markedly reduced in Xenopus single twitch fibers which were previously treated with either 125 mM NaCl or 250 mM sucrose hypertonic Ringer despite the retention of nearly normal action potential and caffeine contracture. This inhibition of excitation-contraction coupling was accompanied by a large reduction in membrane capacity to approximately 2 microF/cm2 during and after immersion in the hypertonic Ringer and can possible be attributed to the same origin of disruption of the transverse tubular system as "glycerol effect."