Thymic involution in rats given diets containing dioctyltin dichloride.

Inbred rats fed diets containing 150 ppm dioctyltin dichloride (DOTC) demonstrated a progressive reduction in thymic weight. This was accompanied by a decrease in both the number of circulating lymphocytes and their ability to respond to mitogenic stimulation. Morphologically the thymuses from treated animals showed a loss of cortical thymocytes and a marked vacuolation of the reticular epithelial cells (REC). After return to normal diet for 4 weeks vacuolated REC were still present and PHA-induced lymphocyte blastogenesis remained low. Adrenalectomy failed to alter the atrophic action of DOTC on the thymus and although administration of hydrocortisone alone produced thymic atrophy, no damage to the REC was observed. The results show that thymic atrophy resulting from DOTC administration differs from that induced by steroids and lends support for the hypothesis that DOTC acts selectively on the thymus in such a way that the humoral function of the organ may be affected.