MODIFICATION OF HEPATOCARCINOGENESIS AND RENAL CARCINOGENESIS BY CATECHOL AND ITS ISOMERS IN RATS PRETREATED WITH N-ETHYL-N-HYDROXYETHYLNITROSAMINE

Modifying effects of catechol, resorcinol, and hydroquinone on second stage hepato- and renal carcinogenesis was investigated in rats pretre ated with N-ethyl-N-hydroxyethynitrosamine(EHEN). Groups of twenty 6-w eek-old Wistar/Crj male rats were treated with 0.1% EHEN in the drinki ng water for 3 weeks. Starting 1 week after the termination of EHEN tr eatment, they were given a diet containing 0.8% catechol, 0.8% resorci nol, or 0.8% hydroquinone or basal diet for 36 weeks. Further groups o f 15 rats were each treated with the same doses of phenolic compounds or basal diet alone without EHEN pretreatment. All surviving animals w ere killed at the end of week 40 when histopathological assessment rev ealed significant reduction of the numbers per rat of hepatocellular a denomas and hepatocellular carcinomas by resorcinol, whereas hydroquin one significantly enhanced the numbers per rat of renal microadenomas and renal cell tumors. On the other hand, the number of alpha2u-globul in positive tubules in the animals treated with hydroquinone was signi ficantly lower than controls, without any alteration in bromodeoxyurid ine (BrdU) incorporation. Lipid peroxidation, as evaluated by thiobarb ituric acid reactive substance (TBARS), was at control levels in the k idneys of rats treated with hydroquinone throughout the experiment. Th e results showed that the known renal carcinogen hydroquinone potently enhances the second stage of EHEN-induced renal carcinogenesis, while its isomer resorcinol inhibited hepatocarcinogenesis. Alpha2u-Globuli n and lipid peroxidation may not play roles in hydroquinone-associated promotion of renal carcinogenesis.