The effect of energy deprivation and hyperosmolarity upon tubular structures and electrophysiological parameters of muscle fibres.

The exhaustion of metabolically poisoned muscle fibres is accompanied by a one hundred-fold increase in potassium conductance. Under these conditions a normal membrane capacity was measured. Extracellular markers (lanthanum, ferritin) were traced in the transverse tubular system but not in the myoplasm or the sarcoplasmic reticulum. These results show that the structural integrity of surface and tubular membranes is fully maintained. The exhausted muscle can, therefore, be introduced as a suitable preparation for an analysis of the potassium channel, the alterations of ion concentrations in the restricted area of the T-system and other phenomena of physiological interest. Further experiments with extracellular markers dealt with the structure of the triads. Earlier measurements by other authors suggested a continuity between lumina of the T-system and the sarcoplasmic reticulum, at least after an exposure to hyperosmotic solutions. These results could not be confirmed.--In addition the distribution of fibre cross areas of sartorius muscle was analysed from cryosections.