Changes of LH, TSH, GH, FSH and PRL in pituitaries and sera of rats after thyroidectomy and thyroxine treatment as studied by radioimmunoassay and disc electrophoresis

Abstract

Rat pituitary hormones (LH, TSH, GH, FSH and PRL) were located in polyacrylamide gels after the separation of rat pituitary homogenate with the aid of electrophoresis. Furthermore, the incorporation of 3H-glucosamine and 14C-leucine into various protein fractions of incubation media and pituitaries incubated for 6 h in vitro, homogenized and then subjected to disc electrophoresis was measured in six groups of rats: 1. control; 2. two weeks after thyroidectomy (Tx); 3.--6. two weeks after thyroidectomy and injected 20 micrograms L-thyroxine (T4) i.p. per animal at 6, 12, 24 and 48 h before sacrifice, respectively. A decrease of 14C-leucine incorporation into GH and PRL after thyroidectomy was found which was improved by T4 treatment. Moreover, an increase of 3H-glucosamine and 14C-leucine incorporation into TSH zone and origin zone was observed, the former presumably representing the extracted TSH and the latter consisting of unextracted portion of TSH, other hormones and unidentified proteins. Such increase was significantly less after T4 treatment. Finally, changes of radioimmunoassayable LH, TSH, GH, FSH and PRL in pituitaries and sera of analogous groups of rats, but consisting of another animals were measured. The content of TSH in the pituitary slightly increased after Tx, but increased further after T4 treatment. In contrast, the content of all other hormones in the pituitary decreased after Tx, while T4 treatment resulted in a stepwise increase. In plasma, a significant decrease of GH and PRL after Tx was found with no remarkable changes after T4 treatment. The level of LH and FSH was unchanged, while that of TSH increased significantly after Tx and sharply decreased to the original level as early as at 6 h after the injection of T4.