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Hormone‐induced modifications of free tyrosine in the rat thyroid gland
Author(s) -
Hodge James V.,
Melmon Kenneth L.,
Sjoerdsma Albert
Publication year - 1969
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1969.sp008845
Subject(s) - thyroid , tyrosine , hormone , endocrinology , medicine , endocrine gland , biology , chemistry , microbiology and biotechnology , biochemistry
The concentrations of free tyrosine in liver, muscle, kidney and thyroid gland were determined in separate groups of rats maintained on a low iodine diet and treated with intraperitoneal injections of thyroxine (T 4), thyrotrophin (TSH) and TSH plus propylthiouracil (PTU). Groups of hypophysectomized rats also were given T 4. Significant changes in tissue tyrosine were generally confined to the thyroid gland. Animals treated with T 4 showed a decrease of mean thyroid tyrosine from 113·3 ± 17·9 ( S.D. ) μg/g wet weight of gland to 76·2 ± 5·7 μg/g ( P < 0·01). Although there was little change in content when TSH was given alone, a significant increase in tyrosine levels was observed when TSH plus PTU were administered ( P < 0·01). In hypophysectomized rats thyroid tyrosine decreased and was further lowered (to 46·0 ± 3·1 μg/g; P < 0·05) by T 4 treatment. When tyrosine concentrations were expressed in relation to ribonucleic acid (RNA) or protein content of the assayed gland, all differences in tyrosine content became greater.