GOLEMAN, W. L.*; GENTLES, B.A.; HU, F.; CARR, J. A.; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock: Evidence that adult frogs are less responsive to the thyroid disrupting effects of ammonium perchlorate.

Recent data suggest that environmentally relevant concentrations of ammonium perchlorate (AP) retard metamorphosis by disrupting thyroid function in larval frogs, but the effect of this contaminant on adult frogs is not known. We exposed sexually mature female Xenopus laevis to environmentally relevant concentrations of AP (38 or 14040 ppb) for 10 wk and examined various aspects of thyroid and reproductive function. Initial histological examination of serially sectioned thyroid glands revealed no evidence of treatment-related thyroid follicular cell hypertrophy or colloid depletion in AP-treated frogs. To confirm these results, thyroid gland cross-sectional area and follicle lumen area were determined quantitatively. No significant between-treatments differences were observed, although there was a trend toward reduced lumen area with increasing AP concentration. We observed no measurable effect of AP on the gonadosomatic index, ovulated clutch size, or plasma estradiol concentrations. Our data suggest that unlike larval frogs, a 10 wk exposure to environmentally relevant concentrations of AP does not significantly affect thyroid function or reproductive status in adult female X. laevis. (Supported in part by the U.S. Department of Defense, through SERDP under a Cooperative Agreement with the USAF, Inst. for Environ, Safety, and Occup. Health, Brooks AFB, TX).