Abstract
1. In order to discuss ‘glycerol effect’ in smooth muscle, an outline of the effect in frog skeletal muscle was described. Since the effect relates functionally and structurally to the excitation-contraction coupling (E-C coupling) process, an introductory description on the structure and E-C coupling in smooth muscle was also made.
2. In a Ringer containing glycerol or urea, contractility of frog stomach muscle decreases and then recovers; upon removing the substances, the contractility is again inhibited and then recovers after the lapse of relatively long time. In response to urea-Ringer, a similar phenomenon occurs also in frog ventricular cardiac muscle.could, thus, be said that the appearance of ‘glycerol effect’ has no relation to the presence or absence of the transverse tubular system in muscle cell.
3. Our preliminary electrophysiological results show that these inhibition of the contractility is due to a disturbance of E-C coupling and Ca-event.
4. Ringer containing glycerol or urea exerts an ordinary hyperosmotic effect frog skeletal, stomach, and ventricular cardiac muscles; nevertheress, the substances exist within cells.
5. Based on these findings, the site in the vicinity of plasma membrane was pointed out as the structure responsible for the inward transmission of excitation for triggering contraction.
