EFFECT OF GLUTATHIONE ON INOSITOL 1,4,5-TRIPHOSPHATE-INDUCED CA2-FED RATS( RELEASE IN PERMEABILIZED HEPATOCYTES FROM CONTROL AND CHRONIC ETHANOL)

The effect of oxidized and reduced glutathione on inositol 1,4,5-trisp hosphate (InsP3)-induced Ca2+ release from endoplasmic reticular Ca2stores was studied in digitonin-permeabilized hepatocytes from chronic ally ethanol-fed rats and pair-fed control animals. The fractional Ca2 + release induced by a subsaturating concentration of InsP3 was signif icantly enhanced in cells from ethanol-fed rats in the absence of a ch ange in maximal InsP3-releasable Ca2+ pool size, and this difference w as not affected by preincubation with reduced glutathione. Incubation with oxidized glutathione (1 mM) increased the efficacy of Ca2+ releas e by subsaturating concentrations of InsP3 in both control preparation s and in cells from ethanol-fed rats. The shift in the InsP3 dose-resp onse curve was not significantly different between the two preparation s. These findings suggest that the enhanced efficacy of InsP3-induced Ca2+ release in hepatocytes from ethanol-fed rats is not caused by the oxidation of protein-bound thiol groups on the InsP3 receptor.