Observations on the regulation of cell volume and metabolic control in vitro; changes in the composition and ultrastructure of liver slices under conditions of varying metabolic and transporting activity.

Liver slices incubated at 1 degree C underwent swelling of both cellular and intercellular compartments, as judged by electronmicroscopy. The ultrastructure showed marked changes, including disorganization of the cytocavitary network and plasma membrane and alterations of mitochondria. Restoration of metabolically favorable conditions (oxygenated medium at 38 degrees C) caused a nearly complete recovery of ultrastructure closely associated with extrusion of water; measurements of inulin space and electronmicroscopy both indicate a recovery of cell volume, with intercellular spaces remaining somewhat expended. The fluid lost was a roughly isotonic solution of Na+ and Cl-, while K+ was reaccumulated in exchange for Na+. Cyanide prevented recovery. Ouabain and oligomycin each partially prevented fluid extrusion, but had little effect on ultrastructural recovery except to induce intracellular vesicles containing particles of thorium dioxide derived from sinusoidal spaces. The vesicles were, however, markedly different in form with each inhibitor. There are, thus ouabain-sensitive and insensitive components of volume regulation; the former appears to depend on the coupled transport of Na+ and K+ and the latter, we suggest, on a secretion of Na+ and Cl- into vesicles which release their contents into the bile canaliculi by an oligomycin-sensitive mechanism. Mitochondria showed conformational changes between orthodox and condensed forms, but these could not be directly related to tissue energy states; the numbers of mitochondrial dense granules bore a closer relation to tissue ATP.