IN VITRO THYROTROPIN-INDUCED PROTEOLYSIS IN THE THYROID GLAND*

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Abstract
The effect of thyrotropin on proteolysis in thyroid slices was studied in vitro at a physiologic pH. After the prior administration of thyrotropin in vivo or its addition in vitro, an increased release of butanol-extractable iodine 131 from prelabeled rat thyroid minces was observed during in vitro incubation. An increase in thyroxin, triiodothyronine, iodotyrosine, and iodide was demonstrated. In beef and sheep thyroid slice studies, thyrotropin produced increases in free alpha-amino nitrogen, tyrosine, and inorganic iodidel27 during in vitro incubation. This increased proteolysis was further shown to be a highly specific thyrotropin-induced effect on its target organ.