2,8-Dihydromirex: a twenty-eight day sub-acute toxicity study in the rat.
Abstract Weanling Sprague‐Dawley rats were randomly assigned to seven groups each containing 5 males and 5 females. The groups were fed diets for 28 days containing the following levels of chemical: group 1, 0; group 2, 0.5 ppm dihydromirex; group 3, 5.0 ppm dihydromirex; group 4, 50 ppm dihydromirex; group 5, 500 ppm dihydromirex; group 6, 50 ppm photomirex; group 7, 50 ppm mirex. At the highest level of dihydromirex, 3 out of 5 male and 4 out of 5 female rats died. Photomirex caused decreased weight gain in both male and female rats. With the exception of animals fed 0.5 and 5.0 ppm dihydromirex, all other groups had increased liver weights. Histological alterations were observed in the livers and thyroids of all treated rats and were dose‐related. The changes in the liver consisted of panlobular ballooning of hepatocytes, anisokaryosis and fatty vacuolation. Changes in the thyroid consisted of a reduction in colloid density with collapse of follicles and an increase in epithelial height. No consistent ...