ACTION IN VITRO OF THYROTROPIC HORMONE AND IODIDE ON THYROID CELLS

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Abstract
Fragments of the thyroid gland of young white rats have been maintained in vitro for as long as 96 hrs. and subsequently studied cytologically with the freezing-drying technique of Altmann-Gersh. The direct action of thyrotrophic hormone and iodide was tested on these explanted prepns. Thyrotrophin strongly increases the amt. of intracellular colloid within 30 mins. of the time of application. It activates secretion of colloid droplets toward the lumen and release of intrafollicular colloid. The released colloid apparently remains in the in-terfollicular spaces and is taken up by macrophages. NaI in a conc. of 0.15 M-0.015 M inhibits the action of thyrotrophin on the secretion and release of the colloid. These results are discussed in view of recent findings bearing on the physiology and enzyme chemistry of the thyroid gland.