Physiological Availability of Iodine in Dithymol Diiodide

Abstract

Radioactive dithymol diiodide (DDI) was prepared from 50 mg. of KI containing 1 milli-curie of I131. DDI corresponding to 0.007% I was mixed with 100 mg. of tricalcium phosphate and added to 10 g. of I-free salt. A second batch of salt was made in which this I content was 100 times the normal amt. The remaining DDI was made into a water slurry of 10 mg./ml. to be given orally to rats. Diet 1 contained salt with 0.007% I; Diet 2 contained salt with 0.7% I. The first pair of rats were starved 24 hrs. and given diet 1. Both rats ate 50 g. of feed and were killed after 36 hrs. A 2d pair of rats were given diet 2. They ate 50 g. of feed and were also killed in 36 hrs. A 3d pair of rats were given a normal diet, but each was given 3 oral doses of 1/3 ml. eacn [degree]f DDI in water. After 36 hrs. the thyroid, kidney, spleen, and liver were removed from each rat, fixed in formalin, washed in alcohol, and dried. Radio-autographs were made of these organs. The thyroids badly overexposed the films, but the other organs produced no effect. It was estimated from the radioautographs that 25 to 50% of the I consumed had concentrated in the thyroid. The results gave graphic evidence that the I in the water-insoluble DDI was physiologically available to the thyroid of the rats.