Cell Water, Sodium, and Potassium in Stimulated Red and White Mammalian Muscles.

SR~TER, F. A. Cell water, sodium, and potassium in stimulated red and white mammalian muscles. Am. J. Physiol. 205(6) : I 2951298. I g63.pPotassium and sodium concentration and inulin space were measured in samples of rat soleus, plantaris, and gastrocnemius muscles after indirect stimulation in situ for 4 min, 30 min, and 6 hr. Two samples were taken from the gastrocnemius muscle : one from its outer layers, containing mostly white fibers, and another from the deep layer containing relatively more dark fibers. The cationic changes which follow low-frequency stimulation are largest in white gastrocnemius fibers? and decrease in this order: plantaris muscle, red gastrocnemius fibers, and soleus. When the stimulation frequency was increased, predominantly red components of the triceps surae also showed a marked cationic “debt.” The same occurred with an intermittent tetanus alternating with stimulation at ~o/sec. Intermittent tetanus alternating with resting periods or continuous tetanus did not cause any significant change in cationic distribution.