Livers of male rats were perfused for 120 min in a recirculating hemoglobin-free system with different concentrations of cyclosporine (CS 2, 10, 50, 150 and 200 mg/l). CS produced damage to the livers in a dose dependent manner. The first sign of hepatotoxicity was a reduction of bile flow amounting to 50% already at 50 mg/l CS. At concentrations of 150 mg/l and 200 mg/l, CS lead to a nearly complete suppression of bile flow, furthermore to a release of cytosolic (GPT, glutamate-pyruvate transaminase, LDH, lactate dehydrogenase) and mitochondrial (GLDH, glutamate dehydrogenase) enzymes into the perfusate and to a decrease in hepatic oxygen consumption (30% at 200 mg/l CS). As a consequence of the reduced aerobic energy supply, hepatic ATP concentration declined (70% at 200 mg/l CS). The hepatic concentrations of reduced glutathione (GSH) were not changed but those of oxidized glutathione (GSSG) increased up to 5-fold by CS. Malondialdehyde (MDA) concentrations in the liver and in the perfusate were not affected consistently by CS. The toxic actions of CS in the isolated rat liver were not influenced (a) by the feeding status of the rats (fed or fasted before surgery) or (b) by addition of superoxide dismutase (SOD, 20 mg/l) and catalase (20 mg/l) to the perfusate 30 min before CS. On the other hand, CS-induced hepatic injury could be attenuated or inhibited completely by addition to the perfusate of (1) 2 mmol/l GSH; (2) 12 mmol/l serine; (3) 12 mmol/l glycine; (4) 0.09 mmol/l deferoxamine (DFO). Conclusions: CS induces cholestasis at lower concentrations, probably by another mechanism(s) than the other signs of hepatotoxicity (enzyme release, ATP depletion). Several lines of evidence indicate a probable participation of reactive oxygen species in CS-induced hepatotoxicity. GSH, DFO, glycine and serine could provide therapeutic opportunities to prevent CS-induced hepatotoxicity in patients treated with high doses of CS.
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