PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P574) Contribution of Ammonium Ions to the Lethality and Antimetamorphic Effects of Ammonium Perchlorate.
Goleman, Wanda*,1, Carr, James1, 1 Texas Tech University, Lubbock, TX, USA
ABSTRACT- Although ammonium perchlorate (AP) inhibits thyroid hormone-dependent aspects of metamorphosis, the relative contribution of ammonium ions to these effects or to AP-induced mortality has not been evaluated. Xenopus laevis embryos were exposed within 24 h of oviposition to a range of ten sodium perchlorate (SP) or ammonium chloride (AC) concentrations for 5 d to determine the ammonium ion contribution to AP lethality. Ammonium chloride was significantly more lethal than sodium perchlorate, with LC50s of 118 ppm and >1,220 ppm, respectively. Ammonium chloride also caused a higher incidence of abnormal swimming and bent axial skeletons. The incidence of edema, however, was lower in both control and AC treated groups compared to SP treated animals. To further ascertain ammonium ion contribution to AP developmental effects, X. laevis embryos were exposed within 24 h of oviposition to two sublethal concentrations (38 and 14,040 ppb) of AC, SP, AP, or untreated FETAX medium for 70 d. Although 14,040 ppb AC reduced snout-vent length, there was no effect observed on thyroid-sensitive metamorphic indices (hindlimb growth, forelimb emergence, tail resorption) while the same concentrations of SP and AP completely inhibited metamorphosis. No treatment-related effects on mortality or abnormal swimming were observed at these concentrations. These data suggest that while ammonium ions may contribute significantly to the lethality of AP, they do not contribute to the effects of AP on thyroid hormone-sensitive indices of metamorphosis in X. laevis. (The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements; either expressed or implied, of the 311 HSW/AFIERA or the U.S. Government. 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).
Key words: anuran, ammonium ion, ammonium perchlorate, endocrine disruption