The Mammary Elimination of Radioiodine

Abstract

Labeled iodocasein was prepared, purified by isoelectric precipitation and freed of NaI. It was given by stomach tube to a lactating rabbit and to 2 lactating goats. In addition, I131 labeled NaI was given by stomach tube to 2 lactating goats. After oral administration of I131 labeled iodo-casein to a lactating rabbit monoiodotyrosine, diiodotyrosine, and I appeared in the milk. Single oral doses of I131 labeled iodocasein to lactating goats resulted in mammary elimination of an average of 15.5% of the given I as iodide. I131 labeled NaI given orally to lactating goats resulted in mammary elimination of an average of 50% of the radioactive I as iodide. In a single experiment, the levels of elimination of orally given NaI131 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 NaI131 was eliminated in the milk of a lactating goat as iodide. A chromato-graphic-radioautographic technique capable of separating monoiodotyrosine, diiodotyrosine, thyroxine, and NaI in skim milk, failed to detect the presence of any I compounds other than iodide in the milk of goats treated with I131 labeled iodocasein or NaI.