The Mammary Elimination of Radioiodine

Summary The oral administration of I 131 -labeled iodocasein to a lactating rabbit resulted in the identification of monoiodotyrosine, diiodotyrosine, and iodide in the milk. The oral administration of single doses to lactating goats resulted in the mammary elimination of an average of 15.5% of the administered iodine as iodide. Oral administration to lactating goats resulted in the mammary elimination of an average of 50% of the administered radioactive iodine as iodide. In a single experiment, the levels of elimination of orally administered sodium iodide 131 in the milk, urine, and feces were 45.3%, 40.7%, and 2.3%, respectively. In a single experiment 31.2% of an oral dose of carrier-free sodium iodide 131 was eliminated in the milk of a lactating goat as iodide. A chromatographic-radioautographic technique capable of separating monoiodotyrosine, diiodotyrosine, thyroxine, and sodium iodide from skimmilk failed to detect the presence of any iodine compounds other than iodide in the milk of goats treated with I 131 -labeled iodocasein or sodium iodide.