THYROID AUTOGRAFTS IN HYPOPHYSECTOMIZED AND IN THYROXINE TREATED RATS

Abstract

SUMMARY Rats were hypophysectomized and the left thyroid lobe auto-implanted subcutaneously to the anterior abdominal wall 3 weeks later. They were killed at intervals varying from 2 to 56 days after implantation. Twelve grafts were identified histologically in the twelve animals in which completeness of hypophysectomy was confirmed by serial section of the pituitary bed, extreme lowering of T/S ratio, marked loss of weight of adrenals and testes and loss of body weight. The follicles of the graft showed taller cells than those in the neck and intracytoplasmic PAS-positive droplets. In a further series of rats production of TSH was suppressed by daily s.c. injections of thyroxine varying from 15 to 100 μg. One thyroid lobe was auto-implanted after 3 weeks' treatment, the thyroxine being continued afterwards. Animals were killed at intervals from 3 to 15 days. Thirty-two grafts were identified in the 36 thyroxine-treated rats. Autoradiographs at 6 and 24 hr. after administration of 50 μc 131I showed a greater iodine uptake in some follicles of the grafts than in any in the neck thyroid at 15 days. Measurement showed thyroid follicular cells in the graft to be twice as tall as those in the neck. It was concluded that the 'take' of thyroid grafts is independent of TSH and that their reparative growth is accompanied by an associated increased organic binding of iodine.