The role of mitochondrial glutathione and cellular protein sulfhydryls in formaldehyde toxicity in glutathione-depleted rat hepatocytes

Abstract

Depletion of cellular GSH by diethyl maleate (DEM) potentiates CH 2O toxicity in isolated rat hepatocytes and it was postulated that this increase in toxicity is due to the further decrease in GSH caused by CH 2O in DEM-pretreated hepatocytes (1). The present investigation was conducted to investigate further the effects of CH 2O, DEM, and acrolein (a compound which is structurally related to CH 2O and DEM) on subcellular GSH pools and on protein sulfhydryl groups (PSH). CH 2O caused a decrease in cytosolic GSH but had no effect on mitocnondrial GSH either in previously untreated hepatocytes or in DEM-pretreated hepatocytes in which GSH was approximately 25% of control. DEM decreased both cytosolic and mitochondrial GSH but it did not produce toxicity. Neither CH 2O (up to 7.5 m m) nor DEM (20 m m) decreased PSH. However, in cells pretreated with 1 m m DEM, CH 2O (7.5 m m) decreased PSH and this effect preceded cell death. Acrolein decreased both cytosolic and mitochondrial GSH and it also decreased PSH significantly prior to causing cell death. CH 2O and acrolein stimulated phosphorylase a activity, indicative of an increase in cytosolic free Ca 2+, by a PSH-independent and PSH-dependent mechanism, respectively. These results suggest that the further depletion of cellular GSH by CH 2O in DEM-pretreated cells is not due to the depletion of mitochondrial GSH. CH 2O toxicity in DEM-pretreated cells is, however, correlated with depletion of PSH. The critical sulfhydryl protein(s) responsible for cell death remain to be more clearly defined.