[Ultrastructure of the corticotrophic cells of the pituitary gland in rat following administration of steroidogenesis-inhibitors and methylprednisolone (author's transl)]

Effect of drugs on pituitary ultrastructure

Various drugs and hormones influence the light microscopic and especially the electron microscopic structure of the anterior pituitary and its tumors. Many structural effects are known only from animal experiments since specimens from human pituitaries are mostly not available. The structure of growth hormone (GH) cells is relatively stable. A massive GH cell hyperplasia is known only in rare cases with growth hormone releasing factor (GRF) excess from tumors. Prolactin cells can be stimulated by drugs, neurotransmitters, and hormones which decrease the dopamine inhibition. Adrenocorticotropic hormone (ACTH) cells are stimulated by stress, some hormones, loss of adrenals, and drugs which activate the alpha 1- and beta-receptors or inhibit the alpha 2-receptors. They are suppressed and changed into Crooke's cells by treatment with glucocorticoids. Thyroid-stimulating hormone (TSH) cells increase in number and size in states for overstimulation especially by thyrotropin releasing hormone (TRH). A decrease results from hyperthyroidism and possibly from somatostatin, L-dopa, and dopamine. Gonadotroph cells transform into castration cells in strongly hyperactive states (gonadectomy, antiandrogens, gonadotropin releasing hormone [Gn-RH]agonists, aminoglutethimide). Special types of pituitary adenomas can be treated with drugs which suppress hormone production and proliferation. Dopamine agonists and somatostatin reduce the tumor size of varying proportions of GH secreting adenomas in acromegaly. Ultrastructurally, a decrease of cytoplasmic and nuclear volume and an increase of lysosomes are found. Bromocriptine and other dopamine agonists are established in the treatment of prolactin secreting adenomas. They induce a shrinkage in many cases. Ultrastructurally, a reduction of cellular and nuclear size, an increase in number of secretory granules and of lysosomes, and a reduction of rough endoplasmic reticulum can be demonstrated.

Ultrastructural morphometry of the rat pituitary intermediate zone after stimulation and suppression

The intermediate zone of the rat pituitary was studied after stimulation for 3 weeks with the adrenostatic drugs metyrapone and aminogfutethimide and after suppression for 3 weeks with the glucocorticoid 6α-methylprednisolone using morphometry by the point-counting method on electron micrographs. After metyrapone, intermediate cells showed a significant (P <.05) increase in volume percentages of the smooth endoplasmic reticulum, the Golgi apparatus, and the lucent immature secretory granules, as well as a significant decrease in the lucent secretory granules, the vacuoles, the lysosomes, and the cell membranes in comparison with the untreated controls. After aminoglutethimide, the volume percentages of the nuclei, the smooth endoplasmic reticulum, and the dense and lucent immature secretory granules were significantly increased in comparison with the controls, whereas the unorganized cytoplasm, the lucent secretory granules, the vacuoles, and the lysosomes were significantly decreased. The morphological changes after both adrenostatic drugs clearly indicate the pathophysiologically expected increase of secretory activity. After 6α-methyfprednisolone, the rough endoplasmic reticulum, the vacuoles, and the lysosomes significantly decreased in comparison with the controls, and the smooth endoplasmic reticulum, the Golgi fields, and the immature secretory granules were increased. These changes cannot be interpreted without certain reservations as the first alterations indicate decreased activity, whereas the increased Golgi fields and immature secretory granules are usually signs of increased secretory activity, which cannot be expected after glucocorticoid treatment. The possible causes are discussed.

Electron microscopical morphometry of GH producing pituitary adenomas in comparison with normal GH cells

GH producing adenomas of patients with acromegaly (undifferentiated acidophil adenomas and well differentiated GH cell adenomas) were studied at the ultrastructural level and analysed morphometrically by the point counting method. They were compared with identically prepared GH cells of normal pituitaries from patients undergoing surgery for metastasizing cancer of the prostate. In the well differentiated GH cell adenomas significantly more points were counted on nucleoli, unorganized cytoplasm, rough endoplasmic reticulum, immature secretory granules, Golgi areas and on the plasma membranes, than in normal GH cells. Comparison of normal GH cells with tumour cells in undifferentiated acidophil adenomas demonstrated significantly larger volumes of nuclei, rough endoplasmic reticulum, Golgi fields, immature secretory granules and of the cell membranes, and also of nucleoli and of the mitochondria. Secretory granules and lysosomes were observed more frequently than in normal GH cells. In a comparison of both adenoma types, the well differentiated acidophil adenomas contained significantly larger volumes of the unorganized cytoplasm, secretory granules and of cell membranes, whereas more points were counted on the rough endoplasmic reticulum and on the mitochondria in undifferentiated acidophil adenomas. The differences between the normal GH cells and the GH cell in undifferentiated adenomas (mainly larger nucleoli, larger volumes of the rough endoplasmic reticulum and the lower volumes of secretory granules) indicate a higher secretory activity in the adenomas. The significant differences between the well differentiated and the undifferentiated adenomas (mainly the increased volumes of mitochondria and of the unorganized cytoplasm in the undifferentiated tumours) indicate a lower grade of differentiation and may be interpreted as signs of increased proliferation.

Ultrastructure and morphometry of ACTH-producing cell in the rat anterior pituitary gland stimulated by lysin-vasopressin and prostaglandin E1

The aim of this study was to investigate the qualitative and quantitative changes of ACTH-cells in the rat after application of a specific and a non-specific stimulus. A CRF-analog (lysin-vasopressin) and a prostaglandin (prostaglandin E1) were used. 40 rats were injected lysin-vasopressin or prostaglandin E1, respectively, for 4 weeks. The pituitary glands were investigated by means of light microscopy, electron microscopy and morphometry. Activation of the ACTH-cells could be observed after use of both substances, the effect of lysin-vasopressin being more intense than that of prostaglandin E1. Enlargement of the nucleus, the cytoplasm and the organelles involved in hormone-production and -transport were found and verified by morphometry. Additionally an increase in number of the cells could be demonstrated. Prostaglandin influenced not only ACTH-cells, but also other cells of the anterior pituitary.

[Light and electron microscopic studies for classification of pituitary adenomas (author's transl)]

85 surgically removed pituitary adenomas were studied by light and electron microscopical and in part immunohistochemical methods. The tumors were histogically classified and reexamined by the ultrastructure. Histochemically the adenomas could be differentiated in acidophil adenomas (1. group, 41%), mucoid cell adenomas (2. group, 6%), and chromophobe adenomas (3. group, 37%) whereas oncocytic adenomas (4. group, 16%) could be identified only in plastic-embedded sections. About half of the acidophil adenomas were highly differentiated and showed structures which correspond to those of normal STH cells (subgroup 1.1). 1 adenoma consisted of cells of prolactin type (subgroup 1.2). The other acidophil adenomas were differentiated to a lower degree and showed no resemblance to the structures of normal acidophil cells. The 5 mucoid cell adenomas were proved to be with all methods highly differentiated adenomas of ACTH-cell type (subgroup 2.1). TSH-cell adenomas (subgroup 2.2) and lower differentiated mucoid cell adenomas (subgroup 2.0) were lacking in our collection. More than one third of the chromophobe adenomas showed well developed endoplasmic reticulum and Golgi complexes. The other had little and small organellas that resemblances to immature stem cells were evident. The oncocytic adenomas were identified in plastic-embedded sections by their fine-granular structures which were based ultrastructurally not on small secretory granules but on closely arranged mitochondrias.

[Pituitary adenomas of patients with galactorrhea. Light and electron microscopic studies (author's transl)]

A collection of 108 surgically removed pituitary adenomas was studied by histologic, immunohistochemical and electron microscopical methods. It included 7 predominantly chromophobe adenomas of patients whose clinical symptoms consisted of a pure galactorrhea. Ultrastructurally, 4 of these adenomas contained little endoplasmic reticulum so that an endocrine activity of the tumors could not be assumed. These cases represented inactive adenomas which probably led to a disturbance of the secretion of prolactin-inhibiting factor by suprasellar extension resulting in stimulation of the non-tumorous adenohypophysis and secondary hyperprolactinemia. Another 3 adenomas consisted of cells that showed histologic and immunocytochemical reactions of the same kind as normal prolactin cells. Electron microscopically, these adenoma cells exhibited a very well developed rough-surfaced endoplasmic reticulum, dilatation of the Golgi complexes, sparsely arranged pleomorphic secretory granules, an increased number of microtubules, and interdigitating microvilli formed by the cell membrane. These features resembled closely the characteristics of stimulated non-tumorous prolactin cells during lactation, and thus could be termed "prolactin cell adenomas". These tumors surely caused a hyperprolactinemia through their own hormone production. In addition 3 other adenomas were present which showed the same light and electron microscopic structures as the prolactin cell adenomas but did not cause galactorrhea. From the findings in these cases we assume that the tumors effected neither a clinically peculiar hyperprolactinemia nor produced an endocrinologically inactive polypeptide.