BIO-ISOMERIZATION OF LINDANE IN RATS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 2  (3) , 737-749
Abstract
The major environmental problem associated with the use of the insecticide .gamma.-hexachlorocyclohexane (.gamma.-HCH, lindane) was the appearance of the more oncogenic .alpha.- and .beta.- isomers as terminal residues in nature. .gamma.-hexachlorocyclohexane must be bioisomerized to the more stable .alpha.- and .beta.-isomers. The effect of dose and duration of treatment on the proposed bioisomerization of .gamma.-hexachlorocyclohexane in the rat was investigated. Weanling female Sprague-Dawley rats were randomly assigned to 1 of 4 groups receiving Purina Lab Chow fortified with 0, 130, 215 or 350 ppm .gamma.-HCH. Six animals from each group were sacrificed after 1, 2, 4, 8, 16 and 24 wk of treatment. Twenty-four h prior to sacrifice all rats received a single oral dose of .gamma.-HCH in peanut oil. There were no significant differences in food consumption or body weights, and no deaths occurred throughout the study. The in vitro dechlorinase activity of the treated rats was significantly higher after 1, 4 and 24 wk of treatment. Except at 4 wk after treatment began, the liver/body weight ratios of the rats fed diets containing 350 and 215 ppm lindane were significantly greater than the controls; while those receiving 130 ppm lindane were significantly greater than the controls after 1 and 2 weeks of treatment. No .beta.-HCH was detected in any of the samples analyzed throughout the study. The levels of .alpha.-HCH found in the adipose tissue after 24 wk of treatment could be accounted for by trace contamination of the lindane used in this study. There was a negative correlation between the hepatic content of .alpha.-, .gamma.-, and .delta.-HCH and duration of treatment. Bioisomerization does not play a significant role in the metabolism of lindane by rats.