Exposure to tributyltin (TBT) via food during developmental stages after weaning, or the exposure via the placenta and their dams' milk, inhibits body weight gain and behaviors in rats

Objectives: Neurotoxicity is one of the major toxic effects of tributyltin (TBT). In our previous study, the mean values of total locomotor distance and instance of wall rearing among others in open field tests of F1 rats exposed to TBT via the placenta and their dams' milk were significantly lower than those in the control. The problem remained to determine the neurotoxic effects of exposure to TBT during the developmental stages after weaning. We, therefore, evaluated the effects of TBT on behavior by continuing exposure from fetus to 9 weeks of age for the comparison with the results among rats exposed to TBT via the placenta and their dams' milk only and rats exposed by their food only. Methods: Male F1 rats were exposed to TBT in utero and postnatally via their dams' milk by the dams' chow containing TBT at 0 and 125 ppm. After weaning, they were either fed chow containing TBT at 0 or 125 ppm until 9 weeks of age. The pups at 9 weeks were composed of the control (control-control: CC), the group exposed by their food only (control-TBT: CT), that group exposed by the placenta and their dams' milk (TBT-control: TC), and the continuous exposure group (TBT-TBT: TT). Open field tests and prepulse inhibition (PPI) tests were performed at 9 weeks of age in F1 rats. Results: In the open field tests, the mean values of total locomotor distance in the CT and TT groups were significantly lower than that in the CC group. For the TC group, the mean value of locomotor distance between 15 to 20 minutes was significantly lower than that of the control. The mean values of instances of wall rearing in the CT, TC, and TT groups were significantly lower than that in the CC group. The mean values of center rearing in the CT and TT groups were significantly lower than that in the CC group. The mean values of face washing in the CT and TT groups were significantly lower than that in the CC group. There were no significant differences in the PPI tests among the groups. Conclusion: These results suggest that TBT exposure during the developmental stages after weaning, as well as the exposure via the placenta and their dams' milk, inhibits the body weight gain and behavior of F1 rats.