A single dose‐response effect of aflatoxin B1 on rapid liver cancer induction in two strains of rats

To investigate rapid liver cancer induction in rats by aflatoxin B1 (AFB1), different single oral doses of AFB1 were given to 3 groups of I‐year‐old Buffalo and Wistar rats. The animals were treated once and all survivors were killed 6 weeks later. Control animals received an equal volume of solvent (DMSO), and both groups of animals were maintained under identical conditions throughout the period of experiment. The survival rates were 40% with low and medium doses in AFB1‐treated Buffalo and Wistar rats, and 0% in the high‐dose Buffalo rats. Slight ante‐mortem elevations in serum concentrations of glutamic pyruvic transaminase (SGOT) and glutamic oxaloacetic transaminase (SGPT) were indicative of the persistent damage effect of AFB1 at week 6. Total protein and albumin concentrations were not altered. The percent incidence of altered cell foci (areas) and neoplastic nodules was higher in Wistar than in Buffalo rats given a similar low dose. Various stages of well differentiated hepatocellular carcinomas (0.1‐0.2 cm in diameter) developed in 3 of 8 Wistar rats. It thus appears that Wistar rats are more susceptible to hepatocarcinogenesis following a single oral dose of AFB1 than Buffalo rats.