ELIMINATION OF RADIOIODINE BY THE SHEEP PAROTID GLAND AFTER [131I]l-TRI-IODOTHYRONINE ADMINISTRATION

Abstract

SUMMARY A study was made of the metabolism of [131I]l-tri-iodothyronine ([131I]T3), in sheep with a unilateral fistula of the parotid gland. After [131I]T3 injection a constant rise in radioactivity in the saliva and a decline in the radioactivity of the serum were found; detectable amounts of radioiodine reentered the circulation from the metabolized hormone after 1 h. Gel filtration showed that the radioactivity in the collected saliva was due to inorganic [131I]iodide. Such an effect might be caused by deiodination [131I]T3 which occurs in sheep parotid glands in vitro. The presence of tracer amounts of hormonal radioiodine in individual sheep could not be excluded. Non-specific deiodinating enzymes may exist in sheep parotid salivary glands.