Growth and developmental effects of exposure to ammonium perchlorate during gestation, lactation, and post-lactation in deer mice

Body weights, organ weights, litter size, litter survival, thyroid hormones, sex hormones, and thyroid and testes histology were evaluated in two consecutive litters of developing deer mice (Peromyscus maniculatus) following in utero and lactational exposure to ammonium perchlorate (AP), a thyroid toxicant. Breeding pairs were dosed continuously wUh either 0, 1 nM, 1 liM, or 1 mM concentrations of AP in drinking water, from cohabitation until pups from the third litter were weaned. Pups from the first litter were weaned at postnatal day (PND) 21 and dosing of the pups continued until PND 70, at which time they were necropsied. Pups from the second litter were necropsied for analysis at PND 21. Body weights in the 1 |iM group were significantly decreased at PND 5 and PND 20 in the PND 21 pups. Body weights in the 1 mM group of the PND 70 pups were significantly increased at PND 5, PND 10, and PND 20. From PND 25 to PND 70, the PND 70 pups showed sex differences. The 1 mM treatment group was significantly increased compared to controls for PND 70 females at PND 25 and PND 50, whereas there were no significant differences in males subjected to the same treatment during this time period. Heart weights were decreased in a dose-dependent manner in PND 21 male pups, but not in females. Heart weights were increased in the 1 mM PND 70 female pups, but no difference was observed in males. No differences were observed in litter size, but the 1 jLiM litter 1 pups had decreased survival percentages. Concentrations of total T4 were significantly increased in the 1 nM and 1 jiM treatments in the PND 21 pups, whereas no significant differences were observed in the PND 70 pups. In contrast, concentrations of total T3 were unchanged in the PND 21 pups, but were significantly decreased in the 1 mM treatment group in the PND 70 pups. The thyroid gland follicle number to thyroid area ratio in the 1 nM, 1 )iM, and 1 mM treatments was significantly increased at PND 70, whereas the 1 nM and 1 mM treatments were significantly decreased at PND 21. These data suggest that AP exposure during mammalian development may cause changes in body weight and alter thyroid gland function, and that these alterations vary depending on the sex and the developmental stage of the animal. These observations raise questions as to the survivability and future reproductive success of juvenile animals exposed to environmental ammonium perchlorate.