3-Methylcholanthrene-Induced Thyroiditis in Buffalo Strain Rats

Abstract

Inbred adult Buffalo strain male and female rats were given 0.033% 3-methylcholanthrene continuously in the diet. They were killed after 4, 8, 12, 16, 24, and 52 weeks. The incidence of rats with thyroiditis tended to increase with continued ingestion of the chemical. The lesion was observed earlier in the female than in male rats, and the incidence increased faster with time on the diet. The most striking finding was the severe thyroiditis (as compared with mild or moderate thyroiditis) in most animals, regardless of when they were killed. It is concluded that the lesion develops “suddenly” rather than progressing from mild to moderate, then severe thyroiditis.