State of water and electrolytes in mammalian cells during maturation and differentiation.

The state of water and electrolytes was examined 1) in the rat erythroblastic leukemic cell, as a model of a maturing erythrocyte; 2) in the mouse Ehrlich ascites tumor cell during the cell cycle as a model of the uninhibited proliferating cell; and 3) in a clonal population of proliferating and differentiating precursor cells cultured from the bone marrow of the rat. Methods used were phenomenological and included assessments of the volumes of osmotically active water, content of K+, Na+, and Cl-, volumes of distribution for Na+, urea, and ethylene glycol, and the thermodynamics of transport of water and solutes into and out of the cell. The erythroblastic leukemic cell provided evidence for compartments of osmotically active and inactive water and solute. The synchronized ascites tumor cell indicated that these compartments varied during the cell cycle. Membrane function as defined by its permeability to water also varied during the cell cycle. When proliferating cells matured, changes in membrane permeability to water and to nonelectrolytes also correlated with successive stages of differentiation.