The Effect of Dioctyltin Dichloride on the Thymus and T-Cell Differentiation in the Rat

Abstract

Various industrial and environmental chemicals have been shown to have a profound effect on thymus and thymus dependent functions (Seinen and Willems, 1976; Vos, 1977; Miller, 1983). Recently, particular attention has been paid to the selective effect of dioctyltin compounds on the thymus. These materials are used extensively in the plastics industry, in particular, during the heat/light stabilisation process in the manufacture of PVC items intended to come into contact with drugs and food stuffs. In 1976 Seinen and Willems reported that dioctyltin dichloride (DOTC) caused a severe reduction of thymic weight in weanling rats after exposure to diets containing 50 or 150 ppm DOTC. Subsequent work in our laboratories indicated that 6–8 week old PVG strain rats were equally sensitive to DOTC. Animals exposed to 75 ppm DOTC via their diet developed overt thymic atrophy after 2 wks exposure (Fig. 1), almost complete atrophy was evident after 4 wks exposure and by 8 wks the thymic remnant consisted almost entirely of brown fat. Body weight gain and food intake were not influenced by the feeding regime and animals showed no signs of abnormal behaviour or appearance. Examination of plastic embedded thymic sections from DOTC treated rats revealed a marked depletion of cortical thymocytes, a concurrent loss of the cortico-medullary junction and an apparent increase in the number of vacuolated reticulo-epithelial cells (RECs).