TRIPHENYLTIN ACETATE TOXICITY - A BIOCHEMICAL AND ULTRASTRUCTURAL-STUDY ON MOUSE THYMOCYTES

1 Triphenyltin acetate (TPTA) has been shown to exert in vivo a select ive toxic effect on the immune system. To assess in vitro possible alt erations induced by TPTA exposure, primary cultures of mouse thymocyte s were incubated up to 24 h with graded amounts (1 - 12 mu M) of the o rganotin. 2 The cytotoxic activity has been evaluated with the MTT col orimetric assay, the neutral red (NR) assay and the lactic dehydrogena se (LDH) cellular release. Cell pellets were fixed with 2.5% glutarald ehyde, resin-embedded and ultrathin sections were observed through tra nsmission electron microscopy. 3 After 2 h of incubation, dose-depende nt increases of cytotoxicity were observed in thymocytes submitted to MTT and NR tests (up to 41.43% and 18.9%, respectively), while 22 h la ter this overt effect on cell viability was noticed merely in cells ex posed to 12 mu M TPTA. Dose-dependent increases of LDH leakage in the culture medium were observed all throughout the study. 4 Morphological investigations revealed features (chromatin condensation, cell membra nes fragmentation and formation of membrane bound apoptotic bodies) su ggestive of apoptosis. 5 This study indicates that TPTA is cytotoxic t o mouse thymocytes: morphologically, the rising of apoptosis is likely to be recognized, as previously reported in different in vitro studie s with other immunosuppressive agents as dioxin and corticosteroids.