Depletion of cellular protein thiols as an indicator of arylation in isolated trout hepatocytes exposed to 1,4-benzoquinone

A method to measure protein thiols (PrSH), reduced and oxidized, was adapte d to determine PrSH depletion in isolated rainbow trout hepatocytes exposed to arylating agent 1,4-benzoquinone (BQ). Toxicant analysis revealed rapid conversion of BQ to 1,4-hydroquinone (HQ) upon addition to hepatocytes. He patocytes exposed to 200 mu M BQ+HQ showed 80% decline in glutathione (GSH) (1 h), 30% loss of PrSH (6 h), and no loss of viability (24 h). Recoverabl e oxidized PrSH was detected only after 24 h (200 mu M BQ+HQ). Exposure to 600 mu M BQ+HQ caused rapid (10 min) loss of > 90% GSH and > 60% PrSH, with eventual cell death. Half of the PrSH depletion at 6 h observed in hepatoc ytes exposed to 600 mu M BQ+HQ was recoverable by reduction with dithiothre itol. Following the loss of GSH in hepatocytes exposed to 600 mu M BQ+HQ, c ellular PrSH were susceptible to direct arylation and oxidation. Rainbow tr out hepatocytes, which contained 10-fold less GSH than rat cells, had a GSH :PrSH ratio of 1:82 compared with rat ratios of 1:2 to 1:6. The methods rep orted are useful for further study and discrimination of reactive modes of action needed for prediction of aquatic organism susceptibility to these ty pes of toxicants.