STRONG PROMOTING ACTIVITY OF PHENYLETHYL ISOTHIOCYANATE AND BENZYL ISOTHIOCYANATE ON URINARY-BLADDER CARCINOGENESIS IN F344 MALE RATS

Post-initiation effects of phenylethyl isothiocyanate (PEITC) and benz yl isothiocyanate (BITC) on hepatocarcinogenesis and urinary bladder c arcinogenesis were examined in rats pretreated with diethylnitrosamine (DEN) and N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). Groups of 21 r ats received a single intraperitoneal injection of 200 mg/kg body weig ht of DEN. Starting 2 days thereafter, they were administered 0.05% BB N in the drinking water for 4 weeks. Three days after completion of th e carcinogen treatment, they were placed on a diet containing PEITC or BITC at a dose of 0.1%, or a basal diet alone for 32 weeks and then k illed for autopsy. Further groups of 6 rats each were similarly treate d with PEITC, BITC or basal diet alone for 32 weeks without prior DEN and BBN exposure. In the liver, although the incidences of liver tumor s were not significantly affected, the multiplicity of foci larger tha n 0.5 cm in diameter was slightly increased by PEITC, In the urinary b ladder, the incidences of papillary or nodular (PN) hyperplasias and c arcinomas were significantly elevated by PEITC or BITC after DEN and B BN initiation. In the groups without initiation, PN hyperplasia was fo und in all rats of both PEITC and BITC groups, along with papillomas a nd carcinomas in some animals, Tumors and PN hyperplasias in the group s treated with PEITC and BITC are characterized by downward growth. Ou r results thus showed PEITC and BITC to be strong promoters of urinary bladder carcino-genesis with some complete carcinogenic potential. (C ) 1998 Wiley-Liss, Inc.