Developmental Exposure to 1.0 or 2.5 mg/kg of Dibutyltin Dichloride Does Not Impair Immune Function in Sprague-Dawley Rats

Organotins are used commercially as pesticides, antifouling agents, and stabilizers for polyvinyl chloride (PVC) pipe. Mono-and di-substituted butyltins, used in PVC pipe production, are of concern to the United States EPA, they leach from supply pipes into drinking water and are reported multisystem toxicants. We assessed immune function in Sprague-Dawley rats after developmental dibutyltin dichloride (DBTC) exposure. Pregnant rats were given drinking water containing 0, 10, or 25 mg/L of DBTC (final concentration) in 0.5% Alkamuls from gestational Day (GD) 6 through weaning of pups (37 days total). Approximate doses to dams: 1 and 2.5 mg DBTC/kg body weight (BW) during gestation, or 2.0 and 4.4 mg DBTC/kg BW while nursing. Litters were sexed, weighed, and culled to 4 males and 4 females per dam on postnatal Day (PND) 2. Beginning on PND3, litters of half of the dams per dose were gavaged with 0, 1.0, or 2.5 mg DBTC/kg BW 3X/week for 10 doses (maternal + direct treatment); remaining litters were exposed indirectly via lactation (maternal treatment). BW of litters exposed to 2.5 mg DBTC/kg BW was 10-20% lower (por = 0.05) relative to other groups from PND14 (males) or PND17 (females) through PND37. Delayed-type hypersensitivity (DTH), antibody synthesis, and natural killer (NK) cell activity were evaluated in immunologically mature offspring (N = 6/sex/group). DTH responses and antibody synthesis did not differ by dose, sex, or exposure. NK cell activity in the 10 mg DBTC/L maternal only group was greater in male offspring than in female. In female offspring from the maternal + direct group, cytotoxicity increased by dose at the 25:1 effector:target cell ratio. Our data suggest that developmental immunotoxicity from DBTC-tainted drinking water is unlikely as the concentrations we used were several orders of magnitude higher than concentrations expected to leach from PVC pipes.