PARENT SESSION
PM24 - Perfluorinated & Perchlorinated Chemicals
Monday, 18 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P424) The Effects of Iodine on Growth and Development of Perchlorate-treated Amphibian Embryos.
Dumont, James*,1, Collier, Joshua1, 1 Oklahoma State University, Stillwater, OK
ABSTRACT- Ammonium perchlorate interferes with iodine uptake by the thyroid by competing for iodine binding sites. We have supplemented perchlorate culture media with iodine (potassium iodide) to examine the effects on amphibian growth, development, and metamorphosis. FETAX studies with Xenopus embryos showed a reduction in embryotoxicity of perchlorate in these early stage embryos. For example, the LC50 for perchlorate is ~575 mg/L. The addition of iodine in concentrations of 0.5, 1.0, and 5.0 mg/L increased the LC50s to 800, 875, and 950 mg/L respectively. The EC50s are increased from 450 mg/L to 525, 500, and 750 mg/L with the addition of iodine in the concentrations noted above. Studies with older Xenopus embryos showed that at 10 and 100 mg/L perchlorate and 1 mg/L iodine, metamorphosis of the iodine-treated embryos was accelerated past the controls. However, at higher concentrations of perchlorte the addition of iodine was embryotoxic. The size (snout/vent length and weight) of metamorphosed forglets from iodine treatments is generally less than that of controls. Tests with Southern Leopard Frog embryos exposed to 1 or 0.5 mg/L iodine showed that at concentrations of perchlorate below 100 mg/L the lower iodine concentration is more effective in stimulating growth and metamorphosis while at concentrations of perchlorate above 100 mg/L, 1 mg/L iodine is more effective. Interestingly, similar tests with Cricket Frog embryos suggested that iodine was not effective at all in mitigating the effects of perchlorate except at higher perchlorate concentrations. This information suggests that there may be significant species differences. Remediation of perchlorate-contaminated environments by the addition of samll quantities of iodine may be possible but species differences are problematic. (Research suppored by the Strategic Environmental Research and Development Program, SERDP)
Key words: perchlorate, iodine, amphibian, metamorphosis