Abstract
Ninety-six male and female rats were injected subcutaneously with 2 mg./kg. of 6-mercaptopurine monohydrate (as the free base) daily from 2 to 22 days of age. An equal number of controls received saline. Clinically, 15 of 77 surviving treated rats exhibited paresis of the hindlegs while 44 (including the 15 with paresis) had flattened croups (gluteal area). Grossly, the gluteal, thigh and lumbar vertebral muscles were markedly atrophied and partially replaced by adipose tissue. Microscopically, the muscles of 50 of 66 treated rats consisted of varying sizes and shaped myofibers which were extensively infiltrated by fat cells. Chains of centrally positioned nuclei, foci of necrosis and inflammation were occasionally observed in the affected muscles. Other regions of the musculature and other organ systems of the treated rats were normal. None of the 77 surviving control rats presented clinical signs, gross or microscopic lesions comparable to the treated rats. The observations presented at this meeting were demonstrated and discussed with respect to their correlations with other clinical, gross anatomical, biochemical and histochemical findings.