Abstract
The effects of the outermost structure of the muscle cells on ionic movements or contents were investigated with reference to the movement of membrane Ca++ when the membrane of the sartorius muscle of the frog or toad was disturbed (1) mechanically by stretch, (2) mechanically by soaking with hypertonic Na Ringer, and (3) chemically by treating with trypsin.1. In Ringer, 130% stretch of the muscle for 24 hours resulted only in a slight increase in internal Na. Ion contents of the muscle, while 140% stretch in trypsin-Ringer, were the same value as those unstretched and in the same solution. Accordingly, stretch in such a ratio caused no morphologically significant changes even after immersion for 24 hours.2 . Hypertonic medium, 200 mM Na, showed the depolarization of 15 - 20 mV and a transient increase in Ca45 efflux. The Ca45 efflux was varied proportionally by changing external Ca concentration. Because this effect of hypertonic Ringer on Ca45 efflux can be additive to Ca45 efflux increase produced by another depolarizing agents the membrane sites from which Ca ions are released in hypertonic solution may be different from the membrane sites which dissociate Ca ions under other conditions.3. Trypsin caused the increase in internal Na and the decrease in internal K, and this pattern resembled the picture of facilitated diffusion which is similar to cation movements observable in K free Ringer. Ionic changes were simultaneously followed by both depolarization and an increase in Na22 fluxes, but no immediate correlation with the dissociation of membrane Ca++ was detected. The changes in trypsin-Ringer were Ca-independent. Although the conditions to demonstrate the membrane depolarization are generally supposed as those which increase Ca45 efflux the treatment with trypsin shows no such close interrelationship.
