IN VITROSTUDIES OF THE INTACT THYROID GLAND*

Early Effects of Thyrotropin on Protein-Bound Iodine131 and Plasma Iodide131*

“…This interpretation of our data in the human is also consistent with experiments of Halmi (13) who found in rats an initial depression of the thyroid to serum (T/S) ratio of iodide'3' following TSH before the increase in T/S was noted. This same interpretation fits equally well with data of others (14,15) showing an actual depression of in vitro uptake of iodide'8' by isolated thyroids of normal rats treated with TSH whereas hypophysectomized rats (presumably thyroglobulin-depleted) similarly treated showed increased uptake. These observations may also explain the differences in rate of iodide uptake as compared with hormone release noted in the literature (5,16) for if the thyroglobulin deficient gland is stimulated by TSH one would anticipate less early inhibition and consequently the uptake of plasma iodide would be greater.…”

Thyroid

“…These appear only after liberation of the iodothyronines. Their activity has been tested in different substrates, and it was found that TSH activates catheptases in vivo (91) as well as in vitro (92). Thyroid proteolysis leading to diffusible products of low molecular weight takes place in the colloid vesicles and is carried out by proteinase systems of a catheptase nature characterized for the first time by de Robertis in 1941 (90) and later confirmed by various authors.…”