Detoxication and bioactivation of endrin in the rat.

1. Rats exhibit a sex difference in the rate of metabolism of endrin. 2. The major metabolite in both sexes is anti-12-hydroxyendrin which is excreted via the bile as the glucuronide. Male rats produce the metabolite at a higher rate than do females. 3. trans-4,5-Dihydroisodrin-4,5-diol is a minor metabolite. A mechanism for its formation is discussed. 4. There is a sex difference in the production and excretion of 12-ketoendrin which is observed as a urinary metabolite in male rat; the major urinary metabolite in female rats is anti-12-hydroxyendrin O-sulphate. 5. syn-12-Hydroxyendrin was not detected but may be an intermediate in the formation of 12-ketoendrin. 6. The formation of 12-ketoendrin is related to the acute toxicity of endrin.