Ultrastructure of STH cells of the pars distalis of castrated male mice after hepatectomy

Electron microscopic immunocytochemistry of prolactin secreting cells (PRL-cells) and growth hormone secreting cells (GH-cells) in the anterior pituitary gland of partially hepatectomized rats

After 60% hepatectomy in rats, prolactin secreting cells (PRL-cells) and growth hormone secreting cells (GH-cells) of the anterior pituitary gland were distinctly identified by the protein A-gold procedure combined with electron microscopy. The animals were sacrificed by the decapitation at midnight at intervals of about 28, 76 and 124 h after the operation. The principal changes can be summarized as follows; (1) Hypertrophy of the Golgi complex, (2) Dilation of the rough endoplasmic reticulum (RER), (3) Increased numbers of secretory granules (markedly in GH-cells), and occurrence of granule extrusion or exocytosis, (4) Increased numbers of lysosomes, which were mostly seen at 124 h after the operation. These ultrastructural changes were remarkably observed in both PRL and GH-cells. Especially, the noticeable changes in PRL-cells after partial hepatectomy in the rat were new findings in this study. The above results suggest that hepatectomy induced synthesis and release of GH and PRL in cells from pars distalis.

Mechanism of the ultrastructural changes induced by partial hepatectomy in the STH cells of mice

The ultrastructural changes induced by partial hepatectomy in the STH cells of mice were examined. These changes suggest an increased secretory activity of STH cells. Therefore, several experimental procedures elucidating the possible mechanism of this effect were undertaken. Normal mice were starved for 52 h or treated with insulin, glucagon, or cAMP. Serum glucose level measurements as well as electron microscopy of pituitary STH cells were carried out in each group of animals. It was found that STH cells of glucagon- and cAMP-treated mice showed some of the ultrastructural features observed in partially hepatectomized animals. Hence, serum hyperglucagonemia and increase in pituitary cAMP content, may be important components of the complex mechanism responsible for the ultrastructural changes in STH cells brought about by partial hepatectomy.

Ultrastructural observaitons of growth hormone (STH) cells of anterior pituitary glands of partially hepatectomized rats

Ultrastructural changes in pituitary growth-hormone cells were observed in partially hepatectomized rats. The hepatectomies were carried out during the afternoon after 3 p.m. The animals were sacrificed by decapitation at midnight at intervals of 32, 80, and 104 hours after the operation. The principal changes in the growth-hormone cells of anterior pituitary glands of partially hepatectomized rats were: (1) increased numbers of secretory granules in exocytosis, (2) increased numbers of microtubules, and (3) enlargement of endoplasmic reticulum and occurrence of dilated cisternae of the endoplasmic reticula. Many growth-hormone cells contained a reduced number of secretory granules. Exocytosis of growth-hormone granules was more frequently observed in animals sacrificed at 32 hours after the operation than in those killed at 80 or 104 hours after surgery. The above results in which appearance of numerous microtubules and active secretory granule extrusion in the growth-hormone cells were observed after hepatectomy indicate that ultrastructure of growth-hormone cells and growth hormone secretion were markedly stimulated by the operation.