Nonelectrolyte distribution in mouse diaphragm muscle. I. The pattern of nonelectrolyte distribution and reversal of the insulin effect

Abstract

The steady-level distribution coefficients ( r values) between the cell water and the incubation solution are measured for a variety of small, hydrophilic, nonmetabolized nonelectrolytes in a red muscle preparation, the mouse diaphragm. Four distinct groups of solutes are discerned: large surgars, with r = 0.08; many monosaccharides, with r = 0.36; some sugars in the presence of insulin at 20 °C, and d-ribose, with r = 0.80; and all compounds tested with four carbons or less, and some sugars in the presence of insulin at 34 °C, with r = 1.00. The results can be interpreted in terms of a four-compartment model of the muscle fiber. The model requires that 64% of the cell volume be noncytoplasmic. The results are considered difficult to interpret in terms of the association-induction hypothesis of Ling. Special conditions are found under which d-xylose moves out of the muscle fiber against its concentration gradient. This observation requires either that insulin-sensitive xylose be adsorbed in the cytoplasm or that an active extrusion mechanism for sugars exists in the muscle.