Autoradiographic Studies on the Distribution of 131I-19-Iodocholesterol in Dogs

The distribution of131I-19-Iodocholesterol in dogs weighing 2.0-2.4kg was investigated by means of whole body autoradiography. Good whole body autoradiogram was obtained in slices of 40-60μ with Cryomicrotome JCMT-IA, which has recently been developed. As animals big in body size were used for examination, small organs such as adrenal gland and thyroid were easily analyzed.131I-19-lodocholesterol accumulated markedly in the adrenal cortex in 168 hrs. after the administration, and it accumulated in the thyroid, too. Continuous administration of potassium iodide (KI) prevented131I-19-Iodocholesterol accumulation in the thyroid, and Iodocasein, which has less side effects, was found to have the similar effects in the blocking of the thyroid.