Action of TSH on thein VivoIncorporation of Labeled Amino Acid into Thyroglobulin and Other Thyroidal Proteins

The incorporation of 3H—tyrosine into thyroglobulin and into the total proteins other than thyroglobulin has been evaluated in thyroid glands 5 hr after the in vivo injection of the isotope into normal, TSH deprived and TSH stimulated animals. Two types of TSH—deprived (hypophysectomy and chronic treatment with thyroxine) and three types of TSH stimulated animals (chronic treatment with methylthiouracil (MTU); hemithyroidectomy and TSH injection into hypophysectomized rats) have been investigated. In the absence of TSH a preferential decrease of synthesis of thyroglobulin was observed; while the stimulation of the synthesis by TSH, did not have a preferential effect on that protein. The TSH increased in the same proportions the incorporation of the isotope into all thyroidal proteins. (Endocrinology92: 1273, 1973)