Whole-Body Autoradiography of the Distribution of ¹²⁵I-Thyrocalcitonin in Mice

¹ Dental Research Center and Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27514, USA

The distribution of ¹²⁵I-thyrocalcitonin in male mice was studied by whole-body autoradiography. At six minutes after injection the highest accumulation of radioactivity was seen in the renal cortex, liver, blood, thyroid gland, bile, and urine. At 20 and 60 minutes there was a rapid decline of radioactivity in the blood and liver and a decided increase in the submaxillary gland, stomach, thyroid gland, urine, and bile. No specific sites of accumulation were noted in bone. Incubation of labeled thyrocalcitonin with mouse serums for as long as 60 minutes revealed significant alteration of the chromatoelectrophoretic properties but no detectable deiodination. Rapid deiodination and degradation of the hormone in blood and other tissues restricted interpretation of the autoradiograms at later time intervals.