S-[(1 AND 2)-PHENYL-2-HYDROXYETHYL]-CYSTEINE-INDUCED CYTOTOXICITY TO RAT RENAL PROXIMAL TUBULES

S-[(1 and 2)-Phenyl-2-hydroxyethyl]-glutathione is nephrotoxic in rats through its metabolic conversion to corresponding cysteine-S-conjugat e, e.g., S-[(1 and 2)-phenyl-2-hydroxyethyl]-cysteine (PHEC). The pres ent study was carried out to determine the mechanism of PHEC-induced t oxicity in isolated rat renal proximal tubules. PHEC decreased tubule viability in concentration (0-2 mM)- and time (0-3 hr)-dependent manne r, with initial decreases occurring 2 hr after exposure. Tubule basal and nystatin-stimulated oxygen consumption decreased before cell death following exposure to 0.5 and 1 mM PHEC. Assessment of direct mitocho ndrial function within the proximal tubules showed that respiration wa s reduced in the absence and presence of a phosphate acceptor using si te II (succinate) and site I (malate/glutamate) respiratory substrates 30 and 45 min after exposure to 0.5 and 1 mM PHEC. Exposure of proxim al tubules to 1 mM PHEC caused a time-dependent decline of mitochondri al membrane potential (as measured by the uptake of the cationic fluor escent dye, rhodamine 123 by the proximal tubules) and depletion of AT P content with initial decrease occurring as early as 30 min after the exposure. Glutathione depletion and lipid peroxidation occurred withi n 90 min clearly preceding cell death after exposure to 0.5 and 1 mM P HEC. Pretreatment with 1 mM deferoxamine prevented PHEC-induced lipid peroxidation but did not prevent PHEC-induced cytotoxicity, whereas de feroxamine pretreatment prevented lipid peroxidation, mitochondrial dy sfunction, and cytotoxicity after exposure to 0.5 mM tertiary-butyl hy droperoxide, suggesting that iron-mediated lipid peroxidation does not contribute to PHEC-induced proximal tubule cell death. Pretreatment o f renal proximal tubules with 10 mM fructose failed to prevent the cha nge in mitochondrial membrane potential, the ATP depletion and cytotox icity caused by 1 mM PHEC, indicating that the glycolytic pathway is n ot important in renal proximal tubule respiration and cell injury. Pre treatment of renal tubules with aminooxyacetic acid failed to prevent the mitochondrial dysfunction induced by 1 mM PHEC, indicating an abse nce of further metabolism of PHEC by a beta-lyase-dependent pathway. I t is therefore proposed that the alteration of mitochondrial functions and the consequent loss of cellular energy supplies can represent the mechanisms by which PHEC expressed its acute cytotoxicity. (C) 1996 A cademic Press, Inc.