Differential regulation of thyrotropin subunit apoprotein and carbohydrate biosynthesis by thyroid hormone

Journal Article · Mon Apr 01 04:00:00 EST 1985 · Endocrinology; (United States)

DOI:https://doi.org/10.1210/endo-116-4-1535· OSTI ID:5675615

Taylor, T; Weintraub, B D

The regulation of TSH apoprotein and carbohydrate biosynthesis by thyroid hormone was studied by incubating pituitaries from normal and hypothyroid (3 weeks post-thyroidectomy) rats in medium containing (/sup 14/C)alanine and (/sup 3/H) glucosamine. After 6 h, samples were sequentially treated with anti-TSH beta to precipitate TSH and free TSH beta, anti-LH beta to clear the sample of LH and free LH beta, then anti-LH alpha to precipitate free alpha-subunit. Total proteins were acid precipitated. All precipitates were subjected to electrophoresis on sodium dodecyl sulfate-polyacrylamide gels, which were then sliced and assayed by scintillation spectrometry. In hypothyroid pituitaries plus medium, (/sup 14/C)alanine incorporation in combined and free beta-subunits was 26 times normal and considerably greater than the 3.4-fold increase seen in total protein; combined and free alpha-subunits showed no specific increase in apoprotein synthesis. (/sup 3/H)Glucosamine incorporation in combined alpha- and beta-subunits in hypothyroid samples was 13 and 21 times normal, respectively, and was greater than the 1.9-fold increase in total protein; free alpha-subunit showed no specific increase in carbohydrate synthesis. The glucosamine to alanine ratio, reflecting relative glycosylation of newly synthesized molecules, was increased in hypothyroidism for combined alpha-subunits, but not for combined beta-subunits, free alpha-subunits, or total proteins. In summary, short term hypothyroidism selectively stimulated TSH beta apoprotein synthesis and carbohydrate synthesis of combined alpha- and beta-subunits. Hypothyroidism also increased the relative glycosylation of combined alpha-subunit. Thus, thyroid hormone deficiency appears to alter the rate-limiting step in TSH assembly (i.e. beta-subunit synthesis) as well as the carbohydrate structure of TSH, which may play important roles in its biological function.

• Research Organization: National Institute of Arthritis, Diabetes, Bethesda, MD
• OSTI ID: 5675615
• Journal Information: Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 116:4; ISSN ENDOA
• Country of Publication: United States
• Language: English

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551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALANINES
AMINES
AMINO ACIDS
ANIMALS
ANTIGEN-ANTIBODY REACTIONS
BIOSYNTHESIS
BODY
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
DISEASES
ELECTROPHORESIS
ENDOCRINE DISEASES
ENDOCRINE GLANDS
GLANDS
GLUCOSAMINE
HEXOSAMINES
HEXOSES
HORMONES
HYPOTHYROIDISM
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
MONOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PITUITARY GLAND
PITUITARY HORMONES
RADIOASSAY
RADIOIMMUNOASSAY
RATS
RODENTS
SACCHARIDES
SYNTHESIS
THYROID HORMONES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TSH
VERTEBRATES