Activation and deactivation of aflatoxin B1 in isolated rat hepatocytes

Isolated rat hepatocytes took up [3H]-aflatoxin B1 during incubation with fifty percent of the aflatoxin B1 covalantly bound to cellular macromolecules. The amount of bound-aflatoxin B1 was proportional to the medium concentration of aflatoxin B1. The specific radioactivity (pmole/mg) of aflatoxin B1 found in the DNA fraction was 20 fold greater than that associated with protein. Metyrapone (0.75 mM) inhibited significantly the uptake and binding whereas 1,2-epoxy-3,3,3-trichloropropane (0.5 mM) enhanced 2-3 fold both the uptake and binding. Glutathione (0.25 mM) reduced these processes. Results indicate that a transformation of aflatoxin B1 is catalyzed by cytochrome P-450 mixed function oxidase and aflatoxin B1-2,3-epoxide so formed is primarily deactivated by epoxide hydrolase. In the isolated hepatocyte depletion of the epoxide by glutathione apparently has an insignificant role in aflatoxin detoxication.