Concentration and persistence of tin in rat brain and blood following dibutyltin exposure during development

Dibutyltin (DBT), a widely used plastic stabilizer, has been detected in the environment as well as human tissues. Although teratological and developmental effects are well documented, there are no published reports of DBT effects on the developing nervous system. As part of a developmental neurotoxicity study of DBT, tissue samples were periodically collected to determine the distribution of total tin (Sn) in brain and whole blood. Pregnant Sprague-Dawley rats were exposed to 0, 10, or 25 ppm DBT in drinking water from gestational day (GD) 6 to weaning at postnatal day (PND) 21. Beginning on PND 3, half of the litters were directly dosed every 2 to 3 d via oral gavage with 0, 1, or 2.5 mg/kg DBT such that the dose level matched the water concentration (for example, litters with 25 ppm DBT in the water received 2.5 mg/kg). For Sn analysis, brain and blood samples were collected from culled pups on PND2 (males and females pooled), from pups (males and females separately) as well as dams at weaning (PND21), and from adult offspring (males and females) at PND93. Total Sn was quantified using inductively coupled plasma-mass spectroscopy (ICP-MS). At all ages, brain Sn levels were higher than blood. At culling, in the directly dosed pups at weaning, and in dams at weaning, Sn levels in both tissues were linearly related to dose. Weanling pups without direct dosing showed lower levels than either culled pups or dams, indicating that lactational exposure was minimal or negligible even while maternal exposure is ongoing. In the adults, Sn levels persisted in brains of directly dosed rats, and the high-dose females had higher levels than did high-dose males. No Sn was detected in adult blood. Thus, during maternal exposure to DBT in drinking water, Sn is placentally transferred to the offspring, but lactational transfer is minimal, if any. Furthermore, Sn is concentrated in brain compared to blood, and its elimination is protracted, on the order of days to months after exposure ends.