Immunohistochemical localization of carboxypeptidases D, E, and Z in pituitary adenomas and normal human pituitary.

Carboxypeptidases may play important role(s) in prohormone processing in normal and neoplastic adenohypophyseal cells of the pituitary. We have recently demonstrated carboxypeptidase E (CPE) and carboxypeptidase Z (CPZ) in the majority of adenohypophyseal cells with carboxypeptidase D (CPD) immunoreactivity largely confined to adrenocorticotrophs. This study evaluated the expression patterns of CPE, CPD, and CPZ immunoreactivity in 48 pituitary adenomas. Our immunohistochemistry demonstrated extensive intracytoplasmic immunoreactivity for CPE, CPD, and CPZ in adrenocorticotrophic hormone (ACTH)-producing adrenocorticotroph cells, prolactin-producing lactotroph cells, and growth hormone (GH)-producing somatotroph cell adenomas, all of which require carboxypeptide processing of prohormones to produce active endocrine hormones. In contrast to the restricted expression in the normal adenohypophysis, CPD appeared to be widespread in the majority of adenomas, suggesting that CPD levels are increased in adenomas. In luteinizing hormone/follicle-stimulating hormone (LH/FSH)-producing gonadotroph adenomas, which do not require carboxypeptidases to produce gonadotropins, only CPZ immunostaining was demonstrated. In null-cell adenomas, CPE immunoreactivity was detected in the majority of tumors, but CPD and CPZ were identified only in a minority of cases. CPE in these cells may process other peptides critical for pituitary cell function, such as chromogranin A or B. These findings suggest that CPs participate in the functioning of pituitary adenomas.     

Endorphin activity in anterior, intermediate, and posterior pituitary.

The content of endogenous morphine-like substance in bovine pituitary and brain was determined by an opiate radioreceptor assay. The intermediate lobe was most concentrated in activity and the brain least concentrated. Most of the endorphin is obtained in a 120 000 g-min fraction from pituitary or brain homogenates.     

Receptor binding, biological, and immunological properties of chemically deglycosylated pituitary lutropin.

Chemical deglycosylation of ovine pituitary lutropin with anhydrous HF has been investigated. Treatment of the hormone for 75 min at 0 °C removed nearly two-thirds of the carbohydrate moiety. Deglycosylation altered the gel filtration and electrophoretic behavior of the hormone. Carbohydrate removal also resulted in dissociation into subunits to the extent of about 20%. In a rat ovarian radioreceptor assay, the deglycosylated hormone derivatives had approximately 35–40% of the binding activity of the native hormone. Immunological activity was fully retained as seen by the gel diffusion method and an α-subunit conformation oriented radioimmunoassay. In collagenase dispersed rat testicular interstitial cells, the derivatives had poor steroidogenic activity (less than 3%) and failed to elicit maximal testosterone production. The deglycosylated derivatives effectively antagonized the steroidogenic activity of the native hormone in rat testicular interstitial cells.     

Basal and potassium stimulated, calcium dependent, endorphins release from pituitary cells.

Mouse pituitary tumor cells grown in tissue culture release endorphins spontaneously to the culture medium. Depolarization of these cells by incubation with high K⁺ concentration (56 mM) increased 2–3 folds the release of endorphins. The K⁺ evoked release was Ca⁺⁺ dependent by that: $\text{a}$, removal of Ca⁺⁺ ions inhibited 90% of K⁺ stimulated release. $\text{b}$, ethyleneglycol-bis (β-aminoethyl ether) N,N′-tetraacetic acid (EGTA) inhibited release of endorphins in the presence of high K⁺ and Ca⁺⁺. It is suggested that dual regulatory system inhibit and/or stimulate $\text{in-vivo}$ release of endorphins from the pituitary glands.     

Pregnancy,prolactin, and pituitary tumours

Nine pregnancies are described in patients with pituitary tumours. All patients had definite radiological evidence of a pituitary tumour and no evidence of acromegaly or Cushing''s disease. In seven patients serum prolactin levels were estimated before pregnancy and found to be raised.Seven patients had been treated with pituitary implantation of yttrium-90. The remaining two developed complications of the tumour during pregnancy. One developed a bitemporal visual field defect in the second trimester which was successfully treated by emergency yttrium-90 implantation. The other developed diabetes insipidus in the third trimester which resolved spontaneously after delivery.Six patients were treated with drugs to achieve pregnancy. Four took bromocriptine to suppress raised prolactin levels, one was treated with human menopausal gonadotrophin, and one was treated with clomiphene.     

Combined stain for fish pituitary.

A new combined stain is described for the study of cell types in the fish pituitary. Tissues are prepared by fixing in formol-sublimate and then embedded in paraffin wax. Tissue is sectioned at 5 micron and than stained sequentially with performic acid-alcian blue, periodic acid-Schiff, orange G, and acid fuchsin. As a result of this procedure acidophils stain as follows: lactotropes, red; corticotropes, light pink; melanotropes, bright pink; and somatotropes, orange. Cyanophils stain either magenta red (gonadotropes) or blue (thyrotropes). Neurosecretory material and the fibers of the pars nervosa which penetrate the pars intermedia stain light blue.     

Human pituitary lutropin. Isolation, properties, and the complete amino acid sequence of the beta-subunit.

The separation of alpha and beta subunits from human pituitary lutropin is described, and the complete amino acid sequence of the beta subunit is proposed. It consists of 115 amino acids with serine and glycine at the amino and carboxyl termini, respectively. The single carbohydrate moiety is linked to asparagine in position 30 and the single tryptophan of the lutropin molecule is located at position 8. The two methionine residues in lutropin-beta are in positions 41 and 42. In addition to COOH-terminal heterogeneity, evidence for internal peptide cleavages was observed.     

Gsh-1, an orphan Hox gene, is required for normal pituitary development.

The anterior pituitary regulates the function of multiple organ systems as well as body growth, and in turn is controlled by peptides released by the hypothalamus. We find that mutation of the Gsh-1 homeobox gene results in pleiotropic effects on pituitary development and function. Homozygous mutants exhibit extreme dwarfism, sexual infantilism and significant perinatal mortality. The mutant pituitary is small in size and hypocellular, with severely reduced numbers of growth hormone- and prolactin-producing cells. Moreover, the pituitary content of a subset of pituitary hormones, including growth hormone, prolactin and luteinizing hormone, is significantly decreased. The hypothalamus, although morphologically normal, is also perturbed in mutants. The gsh-1 gene is shown to be essential for growth hormone-releasing hormone (GHRH) gene expression in the arcuate nucleus of the hypothalamus. Further, sequence and electrophoretic mobility shift data suggest the Gsh-1 and GHRH genes as potential targets regulated by the Gsh-1-encoded protein. The mutant phenotype indicates a critical role for Gsh-1 in the genetic hierarchy of the formation and function of the hypothalamic-pituitary axis.