PHYSIOLOGICAL REACTIONS OF THE THYROIDSTIMULATING HORMONE OF THE PITUITARY I. ITS INACTIVATION BY EXPOSURE TO THYROID TISSUE IN VITRO1

Abstract

Media containing the pituitary extracted thyrotrophic hormone in concs. of 1/4 and 1/2 u. per cc. after exposure to thyroid tissue lost all thyroid stimulating effect and media containing the pituitary hormone in concs. of 1 unit per cc. lost about 7/8ths activity with exposure to in vitro normal rabbit thyroid tissue. Such effects were detd. by the microhistometric method of assay for TSH. Explants of thymic tissue and of lymph nodes completely inactivated the thyroid stimulating effect in concs. of 1/4 u. per cc. and removed about 3/4 of the activity of a medium containing the hormone in a conc. of 1/2 u. per cc. When the hormone was incubated without any tissue in plasma-coated bottles without any tissue or with explants of the following control tissues: adrenal, kidney, liver, ovary, pancreas, parathyroid, spleen, stomach mucosa, and testis, there was not any loss of thyroid stimulating effect. Thyroxin when incubated in soln. with the pituitary hormone removed about half of the thyroid stimulating effect.