Toxicity of triorganotin compounds: comparative in vivo studies with a series of trialkyltin compounds and triphenyltin chloride in male rats.

In 2-week feeding studies, a series of trialkyltin chlorides and triphenyltin chloride were fed to male weanling rats at different dietary concentrations to evaluate their toxic effects, especially on the brains and the lymphoid organs, thymus and spleen. The lower trialkyltin homologs, trimethyltin chloride (TMTC) and triethyltin chloride (TETC), were neurotoxic, causing neuronal degradation and cerebral edema, respectively, at dietary concentrations of 15 ppm. The intermediate homologs, tri-n-propyltin chloride (TPTC) and tri-n-butyltin chloride (TBTC), and the aromatic compound, triphenyltin chloride (TPhTC), caused a dose-related reduction of thymus weight. At a dietary concentration of 150 ppm decreases in thymus weight to 53, 39, and 81% of controls were found following treatment with TPTC, TBTC, and TPhTC, respectively. Microscopically, thymus atrophy was associated with a lymphocyte depletion in the thymic cortex. Only 16% of the total number of nucleated thymocytes could be isolated from rats fed 150 ppm TBTC. These effects were completely reversed within 2 weeks. Slight thymus atrophy was observed after feeding a relatively high dose of 150 mg tri-n-hexyltin chloride (THTC)/kg diet, whereas tri-n-octyltin chloride (TOTC) was ineffective. A dose-related decrease in spleen weight was noticed after 2 weeks feeding of TPTC, TBTC, and TPhTC. Liver weights were increased in rats fed TBTC, THTC, and TPhTC for 2 weeks. Nevertheless, no enlarged livers and normal spleen weights were found upon feeding 100 ppm TPTC or TBTC for 4 weeks, whereas thymus weight was severely decreased. Therefore, atrophy of the thymus was considered to be the predominant effect of the intermediate trialkyltins (TPTC, TBTC). From this study it is concluded that the lower trialkyltins (TMTC, TETC) are essentially neurotoxic, the intermediate trialkytins (TPTC, TBTC) and triphenyltin are primarily immunotoxic, and the higher homologs (THTC, TOTC) are only slightly toxic or not toxic at all.