Glutathione synthetase–deficient lymphocytes and acetaminophen toxicity

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Abstract
Toxic electrophilic metabolites of acetaminophen are detoxified by conjugation with glutathione. Cellular glutathione content of patients with glutathione synthetase deficiency (5-oxoprolinuria) is 10-20% of normal. These patients might be at increased risk for acetaminophen toxicity. The hypothesis was tested by challenging lymphocytes from normals and a patient with glutathione synthetase deficiency in vitro with acetaminophen metabolites generated by a mouse hepatic microsomal drug-metabolizing system. For toxicity to be manifested in normal cells, glutathione content had to be depleted to < 20% of control values at high acetaminophen concentrations (500 and 1500 .mu.g/ml), concentrations similar to blood levels in massive overdose and associated with hepatotoxicity in vivo. The patient''s cells had only 14% of normal glutathione content, and exhibited more toxicity at 12.5 .mu.g/ml acetaminophen (within the therapeutic range) than normals at maximum concentrations. The in vitro system may be of value in screening drugs potentially hazardous for glutathione synthetase-deficient patients, for exploring the role of glutathione in the detoxification of xenobiotics and for examining glutathione protective mechanisms in patients with idiosyncratic cytotoxic drug reactions.