PAPER ELECTROPHORETIC STUDIES ON PITUITARY EXTRACTS FROM NORMAL AND THYROIDECTOMTZED RATS1

Abstract

Paper electrophoretic analysis of saline extracts of rat adenohypophyscal tissue has demonstrated the presence of a protein component which disappeared following thyroidectomy or thiouracil feeding, and was restore:! after thyroxine administration. Since castration and adrenalcctcmy were without effect on this constituent, it is referred to as the “thyroid-labile” component of the adenohypophysis. Extracts of rat anterior pituitary glands which had previously been incubated in vitro in a medium containing lysine-2-C¹⁴ were subjected to paper electrophoresis. Radioactivity was detected in the region of the “thyroidlabile” component. Since the amount of radioactivity in this area was the same in extracts from normal and thyroidectomized rats it was concluded that the isotope had been incorporated into minor protein constituents with mobilities similar to that of the “thyroid-labile” component. Both growth hormone and thyrotropin were localized in the region of the “thyroid-labile” component, but differences in post-thyroidectomy disappearance rates of the hormones and the “thyroid-labile” component were incompatible with the view that the latter might be hormonal in nature. The hypothesis is advanced that the “thyroidlabile” component is related to the acidophilic cells of the adenohypophysis.