7-hydroperoxycholesterol as a marker of oxidative stress in rat kidney induced by paraquat

The in vivo paraquat-induced oxidative stress in rat tissue was studied by analyzing cholesterol-derived hydroperoxide as an index of lipid peroxidati on. Paraquat (10 mg/kg) was administered i.p. to rats. Rats were sacrificed and lung, liver, and kidney were collected 2, 24 h, and 5 d after paraquat injection. Lipids were extracted and analyzed by HPLC with postcolumn chem iluminescence. We found that two cholesterol-derived hydroperoxides, 7 alph a-hydroperoxy-cholest-5-en-3 beta-ol (7 alpha-OOH) and 7 beta-hydroperoxych olest-5-en-3 beta-ol (7 beta-OOH) were present in lungs of control animals (0.06 and 0.06 nmol/g, respectively), in livers (6.5 and 15.8 nmol/g, respe ctively) and in kidneys (3.7 and 8.9 nmol/g, respectively). In liver paraqu at increased lipid peroxidation approximately by 60% over the levels of con trol animals only at 2 h after paraquat treatment. In kidney, augmented lip id per oxidation, 7 alpha-OOH and 7 beta-OOH (by 70% and 147%, respectively ) above levels was found at 2 h after paraquat treatment. Interestingly, th ese increase remained in kidney of rats 5 d after a single dose of paraquat . In contrast, cholesterol-derived hydroperoxides were not affected in lung of paraquat dosed rats. This is the first report on 7 alpha-OOH and 7 beta -OOH accumulations in rat liver and kidney, and it seems to reflect greater oxidative stress in the pathology of kidney of rats treated with acute par aquat at low dose.