THE THYROTROPHIN RECEPTOR IN GUINEA-PIG THYROID HOMOGENATE: GENERAL PROPERTIES

Abstract

SUMMARY Particulate fractions of guinea-pig thyroid homogenate contained a single class of receptors which bound 125 I-labelled bovine thyrotrophin (TSH) by a saturable, reversible process with an affinity constant of 2 × 10 9 1/mol. The binding process was specific for TSH, and corresponded with the activation of adenylate cyclase. Cleavage of hormone—receptor bonds by treatment with lyotropic agents resulted in the release of unchanged labelled TSH. The radioligand receptor assay system was sensitive to 0·015 mu. TSH. Bovine or mouse thyroid showed reduced binding affinity with correspondingly reduced sensitivity.