EFFECTS OF IN UTERO AND LACTATIONAL AMMONIUM PERCHLORATE EXPOSURE ON THYROID GLAND HISTOLOGY AND THYROID AND SEX HORMONES IN DEVELOPING DEER MICE ( PEROMYSCUS MANICULATUS ) THROUGH POSTNATAL DAY 21

Abstract

Thyroid gland hormone levels and histology and sex hormone levels in developing deer mice ( Peromyscus maniculatus ) were measured following in utero and lactational exposure to ammonium perchlorate (AP), a component of rocket fuel and a thyroid toxicant. Breeding pairs were dosed continuously with 0, 1 n M , 1 µ M , or 1 m M concentrations of AP in drinking water from the time of cohabitation until pups from the third litter were weaned. Pups from the second litter were used for evaluation in this study. The active (colloid-containing) thyroid follicle number per unit area was significantly different between treatment groups. The 1-n M and 1-m M treatment groups had significantly fewer active follicles per unit area than did controls. The 1-m M treatment group also had significantly fewer active follicles than the 1-µ M and the 1-n M treatment groups. Total T 4 concentrations were significantly increased in the 1-n M and 1-µ M groups compared to the controls. No significant difference was observed in total T 3 concentrations. None of the 1-m M plasma had concentrations of total testosterone above the detection limit, and only one of the 1-µ M samples was above the detection limit of the assay. All estradiol concentrations were below the detection limits of the assay. In contrast to the situation in adult rodents, it appears that AP increases thyroid hormone production in developing deer mice and produces variable effects with increasing concentrations.