The Biological Significance of Cell Volume

Abstract

To survive, cells have to avoid excessive alterations of their volume. To this end, cells have developed a complex machinery of cell volume regulatory mechanisms comprising transport across the cell membrane and metabolism. Upon cell swelling, they loose electrolytes mainly via selective K⁺ channels and unselective ion channels and/or KCl symport, upon cell shrinkage they accumulate ions by Na⁺, K⁺,2Cl^- cotransport and parallel operation of Na⁺/H⁺ exchange and Cl^-/ HC0₃^- exchange. In addition, cell shrinkage stimulates glycogenolysis, proteolysis and formation of organic osmolytes such as amino acids, methylamines and polyols. Cell swelling stimulates formation of glycogen and proteins and cellular release of organic osmolytes. Alterations of cell volume do play a crucial role in the regulation of cell function, as illustrated by four examples: 1. Epithelial transport may lead to cell swelling, which then triggers volume regulatory mechanisms modifying transcellular transport.2. Insulin swells hepatocytes by activation of Na⁺, K⁺,2Cl^- cotransport and Na⁺/H⁺ exchange, glucagon shrinks those cells by activation of ion channels. The respective volume changes participate in the regulation of cellular protein and glycogen metabolism by these hormones.3. Growth factors and expression of ras oncogene activate Na⁺ , K⁺ ,2Cl^- cotransport and Na⁺/H⁺ exchange leading to the respective cell swelling.4. Hepatocyte swelling triggers a hepatorenal reflex decreasing renal blood flow.

624 Acute Ethanol Exposure Increases the Susceptibility of the Donor Hearts to Ischemia/Reperfusion Injury after Transplantation in Rats

“…doi:10.1371/journal.pone.0049237.g009 cellular swelling. Due to the direct proportionality of the surface area and myocyte volume, the increase in myocyte profile surface area as evidence in the present work with an enlarged cardiomyocytes size 24 h following ethanol exposure indicates cellular swelling [19].…”

Insulin-activated, K+-channel-sensitive Akt pathway is primary mediator of ML-1 cell proliferation

“…These events have been associated with cell cycle progression through G 1 and S phases (6,27,28). Stimulation of mitogens increases expression and activity of K ϩ channels, which has been amply documented.…”

Volume regulation in a toad epithelial cell line: role of coactivation of K+ and Cl‐ channels.

“…The importance of coactivation of Cl-and K+ channels for volume regulation has also been shown in a variety of other cell types, e.g. Ehrlich ascites tumour cells, T-lymphocytes, Madin-Darby canine kidney cells (MDCK), platelets, liver cells and several types of epithelial cells (for reviews, see Lambert & Hoffman 1993;Lang et at. 1993).…”

“…Coactivation of both types of channel is certainly one of the basic mechanisms of RVD. Other mechanisms comprise activation of an electrogenic bicarbonate exit, activation of a K+-Cl-cotransporter, Na+-Ca2+ exchange and Ca2-ATPases, loss of amino acids and cellular polyoles and other mechanisms (Lang et al 1993). In this paper, we give a quantitative evaluation of the transport of osmolytes in toad renal epithelial cells mediated by ionic currents, measured under voltage clamp conditions from cells in which the osmotic gradient during cell swelling is kept constant by dialysing the cell with a solution of constant osmolarity via the patch pipette.…”