The subchronic oral toxicity of the beta-isomer of hexachlorocyclohexane in rats.

The 13-week oral toxicity of beta-HCH, a non-pesticidal isomer of hexachlorocyclohexane, was investigated in rats with doses of 0, 2, 10, 50, or 250 mg/kg feed. Parameters studied comprised clinical signs, growth and food intake, biochemistry, hematology, organ weights, and histopathology. In all dose groups liver effects comprising increase of organ weight, centrilobular hepatocytic hypertrophy, and proliferation of smooth endoplasmic reticulum or increased activity of microsomal enzymes, were observed. In the 50 mg/kg group the weights of thymus and testes were affected. In the highest dose group, progressive clinical signs leading to the unscheduled sacrifice of approximately 50% of the rats were observed. Moreover, in the males of this group atrophy of the testes, characterized by a reduced size of the seminiferous tubules and a decreased number of interstitial cells was observed in association with spermatogenic arrest. The females in this group showed atrophy of the ovaries with impaired oogenesis and focal hyperplasia and metaplastic changes of the endometrial epithelium. These effects are discussed with respect to a possible estrogenic action of beta-HCH.