{'fraction_non_alphanumeric': 0.036101083032490974, 'fraction_numerical': 0.02888086642599278, 'mean_word_length': 4.601010101010101, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Studies on the binding of radiolabeled thyrotropin to cultured human thyroid cells.

A line of cultured human thyroid adenoxna 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 [125I]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 [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 [125I]TSH binding to cells revealed a binding site with a dissociation constant of 5.5 × 10-8 M at pH 7.4. GH, PRL, hCG, FSH, insulin, and glucagon did not compete with [125I]TSH binding. ACTH, however, was a potent inhibitor of [125I]TSH binding. Despite this inhibitory effect on TSH bindin...