Involvement of Ca2(+)-induced Ca2+ release in the volume regulation of human epithelial cells exposed to a hypotonic medium.
Exposure of cultured human epithelial cells (Intestine 407) to a hypotonic solution results in initial osmotic swelling and in a subsequent volume decrease near to the original level. The regulatory volume decrease was inhibited by reduction of the extracellular free Ca2+ concentration to 90 nM. Single epithelial cells responded to a hypotonic challenge with a biphasic increase in the cytosolic free Ca2+ level from about 90 to 200 nM. Both phases of the Ca2+ rise were abolished by reducing the extracellular Ca2+ to 90 nM. In the presence of caffeine (20 mM), the second-phase Ca2+ response to a hypotonic challenge occurred earlier immediately after the first-phase response. The second-phase Ca2+ response was selectively impaired by adenine (10 mM), procaine (1 mM) or ryanodine (5 to 10 microM). These blockers for Ca2(+)-induced Ca2+ release channels inhibited volume regulation after osmotic swelling. It is concluded that Ca2(+)-induced Ca2+ release from a ryanodine-sensitive store is a prerequisite for the volume regulation of human intestinal epithelial cells under hypotonic conditions.
Hazama
A
A
Department of Physiology, Kyoto University Faculty of Medicine, Japan.
Okada
Y
Y
D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology / Q000187:drug effects*; D009994:Osmolar Concentration; D009997:Osmotic Pressure
D002118:Calcium