Excitation-contraction coupling: effects of "zero"-Ca2+ medium.

Frog sartorius muscles, exposed for up to 15--20 min to media containing ethylene glycol bis (beta-aminoethyl ether) - N, N'-tetraacetic acid and thus having free Ca2+ concentration less than 10(-8) M, produce isometric contractions with basically normal but speedier latency relaxation and earliest tension development. The excitation-contraction coupling is thus also basically normal, but speedier evidently in respect to release of activator Ca2+ from the sarcoplasmic reticulum.