Thyroidectomy cells and their response to thyrotrophin releasing hormone (TRH) in the rat

Summary Thyroidectomy cells of the rat pituitary gland were studied by the peroxidase-antibody labeling procedure and by electron microscopy. Secretory granules accumulated in these cells in response to a short-term treatment with thyroxine, and the cells were then reactive to the peroxidase-antibody labeling procedure. An intravenous injection of synthetic thyrotrophin releasing hormone (TRH) to thyroxine-treated, thyroidectomized rats provoked an acute and active extrusion of secretory granules from the thyroidectomy cells. The secretory granules in these cells were mostly haloed after primary fixation in osmium tetroxide. It is concluded that TRH causes thyroidectomy cells to release their secretory granules, and presumably TSH, by the usual process of exocytosis or granule extrusion.This study was supported by USPHS Grant AM 12583.