Studies on binding of radiolabeled thyrotropin to cultured human thyroid cells. [/sup 125/I tracer technique]

Journal Article · Fri Dec 01 04:00:00 EST 1978 · Endocrinology; (United States)

OSTI ID:6777156

Yamamoto, M; Rapoport, B

A line of cultured human thyroid adenoma cells was used in a study designed to compare the stimulatory effect of TSH on cellular cAMP generation with the binding of radiolabeled TSH to the cells. At 37 C, specific binding of (/sup 125/I)TSH to suspensions of thyroid cells was maximal at 20 min and was reversed by the addition of excess TSH. Unlike the generation of cellular cAMP in response to TSH stimulation, which was maximal at pH 7.5, the binding of (/sup 125/)TSH to the cells was maximal at pH 5.5 and progressively declined up to pH 8.5. Increasing NaCl concentrations progressively inhibited cellular binding of TSH; at physiological salt concentrations, almost no TSH binding was detectable. Competitive inhibition studies of (/sup 125/I)TSH binding to cells revealed a binding site with a dissociation constant of 5.5 x 10/sup -8/ M at pH 7.4. GH, PRL, hCG, FSH, insulin, and glucagon did not compete with (/sup 125/I)TSH binding. ACTH, however, was a potent inhibitor of (/sup 125/I)TSH binding. Despite this inhibitory effect on TSH binding, ACTH had little or no effect on cellular cAMP generation. High concentrations of ACTH did not inhibit the biological effect of TSH on cAMP generation. Specific binding of (/sup 125/I)TSH to empty plastic culture dishes was time dependent, reversible, and displayed a hormonal specificity identical to binding to thyroid cells. The effects of pH and NaCl concentrations on TSH binding to dishes were similarbut not identical to those on cellular binding. This study raises serious questions as to the biological significance of (/sup 125/I)TSH binding to cultured human thyroid cells.

• Research Organization: Univ. of California Medical Center, San Francisco
• OSTI ID: 6777156
• Journal Information: Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 103:6; ISSN ENDOA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ACTH
AMP
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
BINDING ENERGY
BODY
CELL CULTURES
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
ENERGY
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPES
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PITUITARY HORMONES
RADIOISOTOPES
THYROID
TSH
TUMOR CELLS