The opiomelanotropinergic neuronal and endocrine systems.

Dans l'hypophyse du rat, la microscopie electronique permet de mettre en evidence a l'interieur de tous les cordons epitheliaux de la pars distalis un reseau de cellules agranulaires: les cellules stellaires et folliculo-stellaires, satellites des cellules granuleuses hormonogenes. Les cellules de ce reseau se caracterisent a la fois par la multiplicite de leurs prolongements et par leur organisation autour de cavites pour la plupart submicroscopiques, «les follicules». Les cellules folliculo-stellaires correspondent a une partie des cellules chromophobes de la microscopie photonique.

[The network of the folliculo-stellate cells and the follicles of the adenohypophysis in the rat (pars distalis)].

Corticotrophin-like peptides in the rat pituitary.

Adrenocorticotropin (ACTH) was localized in the intermediate lobes of normal rat pituitaries with unlabeled antibody and the soluble peroxidase-antiperoxidase complex at the electron microscopic level. All of the intermediate lobe cells (light and dark cells) stained positively for ACTH. Stain of varying intensity was found on secretory granules and vesicles. Structures which resembled rough endoplasmic reticulum stained where the secretory granules and vesicles were most numerous. No stain was on mitochondria, in nuclei, in cisternae and granules of Golgi complexes, or in rough endoplasmic reticulum where there were few secretory granules. There were distinct immunohistochemical differences between the pars intermedia and anterior lobe ACTH cells. In the ACTH cells of the anterior lobe, the Golgi complex and its granules stained strongly, but not at all in the pars intermedia cells. This suggests that ACTH may not be packaged or condensed in the Golgi region of the latter.

Adrenocorticotropin production by the intermediate lobe of the rat pituitary. An electron microscopic-immunohistochemical study

The central nervous system and the pituitary of adrenalectomized male rats injected with 3H-dexamethasone were examined by radioautography. At 1 hr after the injection, radioactivity concentration was high in the medial basal hypothalamus, the pituitary and the pineal gland. In the hypothalamus, radioactive material was found to be selectively concentrated in neurons in the ventral part of nucleus arcuatus and in the infundibular region. In the anterior pituitary, a large proportion of cells showed silver grains both in the cytoplasm and over the cell nuclei. However, in a small number of cells, the radioactive material was associated with the cell nuclei. Less radioactivity was present in the intermediate and posterior lobes. The pineal gland contained more silver grains than did other regions of the brain. The results obtained in the present study suggest essentially an action of dexamethasone in the medial basal hypothalamus and at the level of the pituitary.

Radioautographic study of the rat brain and pituitary after injection of 3H dexamethasone.

In order to identify the cell type responsible for ACTH production in the rat adenohypophysis, the incorporation of thymidine- 3H into the various cell types of the adenohypophysis has been studied using autoradiography. Sections were examined 1 month following adrenalectomy, when ACTH secretion is greatly increased, and 1 month following the daily administration of cortisol, when ACTH secretion is suppressed. Only 1 cell type, restricted to the pars intermedia, responded to altered levels of ACTH secretion with both an increase in label index following adrenalectomy and a decrease in label index following cortisol administration. Histological changes were restricted to the pars intermedia, where numerous dark cells were observed only after adrenalectomy. Following adrenalectomy, increases in weight were restricted to the colloid and the pars intermedia. Since no changes in plasma or hypophysial MSH content were found, the histological and autoradiographic changes do not simply reflect alterations in MSH ...

J. L. Gosbee

Papers

Functional relationship between the pars intermedia and ACTH secretion in the rat.