Radioiodine Metabolism in the Beagle Dog

Abstract

Summary

Seven parameters associated with ¹³¹I whole-body retention and thyroid uptake-retention were chosen to characterize iodine metabolism in the beagle. No statistically significant differences in these parameters were observed in groups of beagle dogs ranging in age from 6 to 48 months. The 6-month-old dogs may have been too old to demonstrate a period of elevated thyroid function such as that reported for several other species. The influence of the mode of administration of ¹³¹I on the resulting iodine metabolism was also investigated. Exposure of 18-month-old dogs to ¹³¹I by the oral, inhalation, or intravenous injection routes produced no statistically significant differences in ¹³¹I metabolism, probably because of extremely short pulmonary retention times and the solubility of the iodide ion in body fluids. Absorbed doses to the thyroid for dogs in this investigation ranged between 130 and 1700 rads. When these doses were expressed as rads per microcurie of initial body burden, an analysis of variance showed that similar thyroid doses per microcurie administered were experienced by all dogs in the experiment regardless of age or route of ¹³¹I exposure. The average dose administered was 5.8 rads/μCi.