lnitiation and post-initiation chemopreventive effects of O-carotene in toad liver carcinogenesis

Abstract

Hepatocellular carcinoma were recognized in the toad, Blfo iliridis, in 14 cases out of 50 by injection of 1 mg 7,12 dimethylbenz(a)anthracene (DMBA)/toad twicelweek for 12 weeks. In contrast, toads treated with DMB at the same dose level and B-carotene (BC), 0.05 mg (3 hr prior to the carcinogen)/toad, twicelweek for 12 weeks showed no tumor incidence. However, BC at the same dose level was less effective when administered 3 hr. after the carcinogen (DMBA). In 8 cases out of 50 cases neither tumor growth nor neoplastic changes were observed in toads treated with BC alone or olive oil. It is concluded that BC completely blocked hepatocarcinogenesis in toads when given 3 hr. before initiation.