Nonelectrolyte distribution in mouse diaphragm muscle. II. cell volume, dxylose distribution, and the effect of insulin in hypertonic solutions

Abstract

The d-xylose equilibrium distribution ratio ( r value) and the relative cell volume are measured in the mouse diaphragm muscle at 34 °C in incubation media made hypertonic with varying concentrations of d-xylose. Under basal conditions, r increases with external xylose concentration, and the muslce fiber shrinks. The xylose r value does not rise if the muscles are shrunken by hypertonic addition of NaCl or mannitol instead of xylose. In the presence of insulin, both r and the cell volume remain constant as external xylose is increased. All observations conform quantitatively to the a priori predictions of the compartmentation theory of sugar exclusion and insulin action. The data contradict predictions of the association-induction hypothesis. The results indicate strongly that intracellular water behaves like normal water aqueous solution and that no significant amount of intracellular xylose is adsorbed. The results also suggest that sugars are excluded from intracellular compartments via an active extrusion mechanism and that insulin causes inhibition of this mechanism.