TOXICOLOGY AND APPLIED PHARMACOLOGY 107,73-80 ( 199 1) Mitochondrial Dysfunction Is an Early Event in Ochratoxin A but Not Oosporein Toxicity to Rat Renal Proximal Tubules MICHAEL D. ALEO,* ROGER D. WYATT,? AND RICK G. SCHNELLMANN*$’ *Department of Physiology and Pharmacology, College of Veterinary Medicine, TDepartment of Poultry Science, College of Agriculture, SDepartment of Pharmacology and Toxicology, College of Pharmacy, University of Georgia, Athens, Georgia 30602 Received May 21, 1990; accepted September 17, 1990 Mitochondrial Dysfunction Is an Early Event in Ochratoxin A but Not Oosporein Toxicity to Rat Renal Proximal Tubules. ALEO, M. D., WYATT, R. D., AND SCHNELLMANN, R. G. (199 I). Toxicol. Appl. Pharmacol. 107, 73-80. Ochratoxin A (OA) and oosporein (OSN) are two my- cotoxins that may cause nephrotoxicity through either mitochondrial dysfunction or lipid per- oxidation. Using isolated rat renal proximal tubules in suspension, the cellular events preceding OA- or OSN-induced cytotoxicity were investigated. OA and OSN decreased tubule viability in a concentration (0- 1 mM)- and time (O-4 hr)-dependent manner, with initial decreases occurring I hr after exposure. Tubule basal and nystatin-stimulated oxygen consumption decreased before cell death alter OA (0.5 and 1 mM) and 0.25 mM t-butyl hydroperoxide (TBHP) exposure, but did not decrease after OSN exposure (0.25-l m&Q. The oxidant TBHP was used as a positive control in these studies. Direct probing of mitochondrial function within proximal tubules con- firmed the toxicity of OA to mitochondria. Respiration was reduced in the absence and presence of a phosphate acceptor using site I (glutamate/malate) and site II (succinate) respiratory substrates I5 and 30 min after exposure to 1 mM OA. Lipid peroxidation preceded cell death after exposure to 1 mM OA and 0.25 mM TBHP, but did not occur after exposure to 1 mtvt OSN. Deferoxamine (1 mM) pretreatment before the addition of 1 mM OA or OSN prevented OA-induced lipid peroxidation, but did not prevent OA- or OSN-induced cytotoxicity. In contrast, deferoxamine pretreatment prevented lipid peroxidation, mitochondrial dysfunction, and the loss of tubule viability after exposure to 0.25 mM TBHP. This study shows that mitochondrial dysfunction is an early event during the development of OA toxicity, but not in OSNinduced toxicity. Fur- thermore, iron-mediated lipid peroxidation does not contribute to OA- or OSN-induced proximal tubule cell death. 0 1991 Academic press, IIK. Human and animal health can be adversely affected by consuming agricultural products contaminated with mycotoxins. The health risks associated with exposure to these sec- ondary fungal metabolites range from carci- nogenesis to acute organ toxicity and mortal- ity. For example, ochratoxin A (OA), a mycotoxin produced by Aspergiilus and Pen- icillium (Cole and Cox, 198 1) has carcinogenic (Kanisawa and Suzuki, 1978) and nephrotoxic potential in animals (Bemdt and Hayes, 1979; ’ To whom correspondence should be addressed. Kane et al., 1986). Epidemiologically, its per- sistence in the food chain has made it the most probable cause of Balkan nephropathy, a fatal nephritic syndrome in humans (Krogh et al., 1977; Pavlovic et al., 1979). Although OA has toxic effects on the renal proximal tubule in numerous animal species (Suzuki et al., 1975; Dwivedi et al., 1984; Brown et al., 1986), a mechanism of toxicity has not been deter- mined. The nephrotoxic potential of OA may be related to mitochondrial dysfunction since OA inhibits respiration in isolated rat liver mitochondria (Moore and Truelove, 1970; 73 0041-008X/91 $3.00 Copyright 0 1991 by Academic Press Inc. All rights of reproduction in any form resewed.