CHEMOPREVENTIVE EFFECTS OF TAURINE ON DIETHYLNITROSAMINE AND PHENOBARBITAL-INDUCED HEPATOCARCINOGENESIS IN MALE F344 RATS

Modifying effects of taurine, a naturally occurring organosulfur compo und, on diethylnitrosamine (DEN) and phenobarbital (PB)-induced hepato carcinogenesis were examined in rats. Male F344 rats, 5 weeks old, wer e divided into 8 groups. Rats of groups 1 through 5 were given i.p. in jections of DEN (100 mg/kg body weight) once a week for 3 weeks from o ne week after the start of the experiment. Of them, animals of group 2 received taurine mixed in a basal diet at a concentration of 2000 ppm for the initial 4 weeks, and those of groups 3 and 5 were given the a gent starting 4 weeks after the beginning of experiment until the end (24 weeks). Rats in groups 1, 4, 7 and 8 were kept on the basal diet t hroughout the experiment (24 weeks). Group 6 was given taurine through out the experiment and group 8 was treated as a vehicle control. Anima ls of groups 1, 2, 3 and 7 received PB in drinking water at a dose of 500 ppm from one week after the end of carcinogen or vehicle treatment . Liver neoplasms were recognized only in DEN-treated groups. The inci dence and average number of liver neoplasms of group 3 were significan tly lower than those of group 1. The number of glutathione S-transfera se placental form (GST-P)-positive foci of group 2 or 3 was significan tly smaller than that of group 1 (P < 0.01 or P < 0.005). The average and unit areas of GST-P-positive foci in groups: 2 and 3 were also sig nificantly smaller than those in group 1 (P<0.005 and P<0.0001, P<0.00 01 and P<0.001, respectively). In this study, the level of ornithine d ecarboxylase activity in non-neoplastic liver tissue was reduced by ta urine treatment in both the initiation and postinitiation phases. Thes e results suggest that taurine could be a chemopreventive agent for li ver neoplasia.