EVALUATION OF THE POSTINITIATION EFFECTS OF OLTIPRAZ ON AFLATOXIN-B(1)-INDUCED PRENEOPLASTIC FOCI IN A RAT MODEL OF HEPATIC TUMORIGENESIS

Previous studies have demonstrated that ingestion of 5-(2-pyrazinyl)-4 -methyl-1,2-dithiole-3-thione (oltipraz) during the aflatoxin B1 (AFB, ) treatment phase completely prevented hepatic cancer. In this study w e evaluated the effect of feeding oltipraz during the post-AFB1 treatm ent phase. Fifty-five male F344 rats were divided into five groups. Al l rats were gavaged with 25 mug AFB1/rat, five times a week for two su ccessive weeks. The rats were fed the oltipraz-supplemented diet accor ding to three different feeding regimes: during the AFB1 treatment pha se (1 week prior to, during and 1 week after the last gavage with AFB1 ); during the post-treatment phase; or throughout the entire time of t he experiment. Phenobarbital-supplemented diet was fed during post-tre atment phase to one group and this was used as a positive control for the promotion of AFB1-induced focal growth. The burden of putative, pr eneoplastic, hepatic glutathione S-transferase P-positive foci was eva luated at 13 weeks after the AFB1 treatment phase. As seen previously, oltipraz fed during the AFB1 treatment phase significantly inhibited focal development, i.e. the volume percent of the liver occupied with foci was reduced by 87%. Oltipraz when fed during the post-treatment p hase neither inhibited nor enhanced focal development.