Cell Volume and Hepatic Metabolism

Abstract

Cell volume homeostasis is crucial for overall cellular function. A great variety of volume regulatory mechanisms has been disclosed and found under appropriate conditions in almost every cell under study (see Chap. 1, this Vol.). These mechanisms are not only activated in order to compensate for cell volume deviations as induced by anisoosmotic exposure or during cumulative substrate uptake into the cell, but they can also be activated in the resting state by hormones so that new steady states of cell volume are generated. Accordingly, cell volume homeostasis does not mean the absolute constancy of cell volume, but rather the integration of events allowing cell volume changes to play a regulatory role in cellular function. Indeed, rapid and persistent cell volume changes may occur physiologically on a short-term time scale. Specifically in the liver, cellular volume can change considerably within minutes following physiological alterations of the hormonal and substrate milieu. Recently, it became clear that such alterations of cell volume markedly influence a variety of metabolic pathways. It appears that cell swelling and cell shrinkage lead to certain opposite patterns of cellular metabolic function. Apparently, hormones and amino acids can trigger these patterns simply by altering cell volume and it was suggested that cell volume alterations may represent a new principle of metabolic control (Haussinger and Lang 1991a,b).