Inhibition of human hepatic glutathione S-transferase isozymes by ethacrynic acid and its metabolites.

The comparative inhibition of ethacrynic acid (EA) and its known metabolites against glutathione S-transferase (GST) was investigated using human livers procured from kidney donors. EA and all three metabolites of EA had an inhibitory effect against conjugation between 1-chloro-2,4-dinitrobenzene (CDNB) and glutathione (GSH). The GSH adduct of EA (EA-GSH) was the most potent inhibitor of GSTs; EA-GSH was approximately one order of magnitude more potent than the parent EA, while L-cysteine conjugate of EA (EA-cysteine) and N-acetyl-L-cysteine conjugate of EA (EA-mercapturate) were approximately two orders of magnitude less potent than the parent EA. Further metabolism of EA-GSH conjugate is suggested to be a detoxification process in terms of GST activities.