BETA-CAROTENE INHIBITS RAT-LIVER CHROMOSOMAL-ABERRATIONS AND DNA CHAIN BREAK AFTER A SINGLE INJECTION OF DIETHYLNITROSAMINE

beta-Carotene (BC) has recently been found to possess potent anti-tumo ur activity in chemically induced rat liver carcinogenesis. In the pre sent study, attempts have been made to understand the basic cytogeneti c and molecular mechanism of the anti-tumour effect of BC by monitorin g its effect on rat liver chromosomal aberrations (CAs) and DNA chain breaks during the early preneoplastic stage of diethylnitrosamine (DEN )-induced hepatocarcinogenesis in male rats. DNA chain breaks, however , can be detected with great sensitivity by exposing crude cell lysate s to alkaline solutions and monitoring the rate of strand unwinding so that one strand break per chromosome can easily be detected. Suppleme ntary BC, in basal diet (120 mg kg(-1)), was given to rats 15 days bef ore carcinogenic threat with DEN. Under these experimental conditions, sc was found to afford a unique protection against DEN-induced CAs 96 h after DEN injection. Long-term treatment with BC also triggered a p rotective effect on induction of CAs 15, 30 or 45 days after DEN treat ment, which was maximal on structural aberrations followed by numerica l and physiological types. BC treatment for 15 days before DEN injecti on was found to offer a significant (P < 0.001) protection in the gene ration of single-strand breaks compared with DEN control. Thus, BC ran ks as a potential chemopreventive agent for the future so far as chemi cal rat liver carcinogenesis is concerned.