Galanin in pituitary adenomas

Tumor galanin content was measured in extracts from human pituitary adenomas using a specific RIA method for monitoring human galanin. Twenty-two out of twenty-four tumors contained galanin with notably high levels in corticotroph adenomas, varying levels in clinically inactive tumors, and low levels in GH secreting adenomas. Tumor galanin and ACTH contents were closely correlated in all tumors. In four young patients with microadenomas and highly active Mb Cushing tumor galanin was inversely related to tumor volume. The molecular form of tumor galanin, studied with reverse-phase HPLC, was homogeneous with the majority of tumor galanin coeluting with standard human galanin. In the tumors analysed with in situ hybridization there was a good correlation between galanin peptide levels and galanin mRNA expression. In some tumors galanin mRNA and POMC levels coexisted, in others they were essentially in different cell populations. Levels of plasma galanin-LI were not related to tumor galanin concentration, and galanin levels were in the same range in sinus petrosus close to the pituitary venous drainage as in peripheral blood. Corticotrophin releasing hormone injections in two patients caused ACTH, but no detectable galanin release into sinus petrosus. Our results demonstrate that corticotroph, but not GH adenomas, express high levels of galanin, in addition to ACTH, and that in some tumors both polypeptides are synthesised in the same cell population. However, galanin levels in plasma were not influenced by the tumor galanin content.     

Human osteoblast-like cells in three-dimensional culture with fluid flow

In a previous study, we showed that the combination of appropriately designed three-dimensional (3D) microcarrier scaffolds and fluid flow through and around the scaffolds during high aspect ratio vessel (HARV) rotation enhances the elaboration of mineralized bone matrix by osteoblast-like cells. In this study, we describe the ongoing characterization of our 3D culture system, including the investigation of interior fluid flow within the scaffolds and early stage integrin expression during hydrodynamic culture. Using theoretical and experimental methods, we have estimated that cells cultured on the interior of microcarrier scaffolds experience an interior nutrient flow velocity between 1 x 10(-3) and 1 x 10(-2) cm/s and maximum shear stress of 0.03 N/m(2). Under these conditions, osteoblast-like cells grew extensively in the interior regions of the scaffold and retained their osteoblastic phenotype as measured by alkaline phosphatase. In addition, flow cytometric analysis of the overall cell population showed that cells constitutively expressed integrin alpha3beta1 during 3D hydrodynamic culture.     

New medical approaches in pituitary adenomas

Recently, the medical approach to patients with secreting and clinically non-functioning pituitary adenomas has received great impulse thanks to the availability of new, selective and long-lasting compounds with dopaminergic activity, such as cabergoline, and of somatostatin analogues provided in slow-release formulations, such as lanreotide and octreotide long acting release (LAR). In particular, the use of cabergoline has induced control of hyperprolactinaemia and tumour shrinkage in the great majority of patients with micro- and macroprolactinomas. Cabergoline treatment restores fertility both in women and men, and partially improves osteoporosis, one of the major complications of hyperprolactinaemia. In acromegaly, disease control (growth hormone [GH] <2.5-1.0 microg/l as a fasting or glucose-suppressed value, respectively, together with age-normalised insulin-like growth factor [IGF]-I) is achievable in more than half of patients receiving treatment with lanreotide or octreotide-LAR. Improvement in cardiomyopathy, sleep apnoea and arthropathy has been reported during GH/IGF-I suppression after pharmacotherapy. A synthetic GH analogue, B2036-PEG, that antagonises endogenous GH binding to its receptor-binding sites and a GH-releasing hormone antagonist that blocks the effect of this releasing factor on the hypothalamus and pituitary are presently under investigation in acromegaly. Preliminary studies have clearly demonstrated the effectiveness of the GH receptor antagonist in suppressing IGF-I levels in acromegalic patients previously unresponsive to somatostatin analogues. Beneficial effects of subcutaneous octreotide and lanreotide have also been reported in adenomas secreting thyroid-stimulating hormone, while the results of treatment with dopamine agonists or somatostatin analogues remain disappointing in patients with clinically non-functioning adenomas. In these patients the possibility of visualising in vivo the expression of D(2) receptors using specific radiotracers such as (123)I-methoxybenzamide has allowed selection of patients likely to respond to cabergoline. Scant effects of pharmacotherapy have also been reported in patients with adenomas secreting adrenocorticotropic hormone. However, some preliminary data suggest a potential use of cabergoline in combination with ketoconazole, or alone, in selected cases of Cushing's disease or Nelson's syndrome.     

Kallikrein- and prolactin-producing cells in the rat anterior pituitary are the same

Kallikrein-positive cells in the anterior pituitary of female rats were identified to be the same as prolactin-producing cells by using an immunoelectron microscopic method. The kallikrein immunoreactivity was localized at the Golgi apparatus, the rough endoplasmic reticulum, and secretory granules, suggesting that kallikrein is synthesized in the prolactin-producing cells and also may be secreted into the blood vessels.     

Intermediate filament expression in pituitary adenomas.

Seventy-five formalin-fixed and 18 alcohol-fixed pituitary adenomas were studied immunohistochemically using antibodies to keratin, vimentin, neurofilaments (NFs), glial fibrillary acidic protein, desmin, actin, S-100 protein and a variety of pituitary hormones. The pituitary adenoma cells were positive for keratin, vimentin and NFs (68 kDa and 160 kDa) and in a few instances there was co-expression of these three types of intermediate filaments (IMFs). The pattern of keratin-specific staining showed diffuse cytoplasmic or patchy paranuclear reactivity and of NF- or vimentin-specific staining showed fibrillar or patchy paranuclear reactivity. The patchy staining seemed to decorate the fibrous body. There was no correlation between the distribution of IMFs and pituitary hormones in pituitary adenomas except that melanocyte-stimulating-hormone-positive reactivity was limited to the NF-positive adenomas. The pattern of IMF staining did not depend on hormone production in adenomas.     

Receptors and neurohormones in human pituitary adenomas

In order to go further into the pathogenesis of human pituitary adenomas, we studied receptors for neurohormones (thyroliberin, TRH; dopamine, DA; somatostatin, SRIH), for estradiol and epidermal growth factor (EGF) thought to influence hormone secretion and/or cell growth. The following results were obtained: (1) the receptors listed above, with the exception of EGF receptors in the adenomas, are present in normal pituitary tissue and in prolactin (PRL)- and growth hormone (GH)-secreting adenomas; (2) they are functional and their affinities are not different in normal or tumoral tissues; (3) their density is variable and depends on the type of secreting adenoma (GH or PRL), the size of the tumor and the plasma level of the hormone which is secreted, and (4) in nonsecreting adenomas, only TRH receptors are found with characteristics identical to those observed in secreting adenomas. We also showed that TRH is contained in normal and tumoral pituitary tissues. TRH and SRIH are released in vitro from adenomatous cells in large amounts, suggesting their possible synthesis by the pituitary. In both cases a local regulation is observed. TRH release is stimulated in the presence of DA while SRIH is inhibited in the presence of TRH. This neuropeptide release may be implicated in the pituitary hormone regulation through a paracrine or an autocrine mechanism. Thus, the neurohormone receptors found in pituitary adenomas should be dependent on a more complex regulation than it has been envisaged till now.     

Adrenomedullin expression in pituitary adenomas and nontumoral adenohypophyses

Adrenomedullin (ADM) is a novel peptide originally identified in extracts of human pheochromocytoma. It is produced by several tissues, including the pituitary gland. The presence of ADM has been immunohistochemically demonstrated in pathologic pituitary glands, but no systematic study of ADM expression in human pituitary adenomas has been reported. Thus, we investigated ADM immunoexpression in 88 various hormone-secreting and clinically nonfunctioning pituitary adenoma types as well as 30 nontumoral adenohypophyses. Furthermore, ADM immunoreactivity was assessed on a 0 to +3 scale in all samples. We found strong immunoreativity for ADM in normal gonadotrophs also expressing FSH and LH whereas in the other adenohypophysial cell types expression of ADM was mild. Results showed that normal adenohypophyses were strongly immunopositive for ADM (2.18+/-0.11). Our findings demonstrate that ADM expression in the anterior pituitary is diminished in tumors as compared to the normal gland. The physiologic function of ADM is unknown, but it could act as a paracrine or autocrine factor in the adenohypophysis.     

Immunohistochemical detection of folliculo-stellate cells in human pituitary adenomas

In the light of recent findings concerning the presence of S-100 antigen in folliculo-stellate cells of the rat adenohypophysis, we investigated the possible presence of S-100-labelled cells in both the normal human adenohypophysis and in pituitary adenomas. Immunostaining enabled us to detect, with both light and electron microscopy, the presence of S-100-labelled folliculo-stellate cells in a significant number of pituitary adenomas, mostly growth-hormone secreting, and, as expected, in the normal human adenohypophysis.     

Annulate lamellae in adenomas of human pituitary glands.

Twelve nontumorous adenohypophyses and 36 various pituitary adenomas, removed by surgery, have been investigated by electron microscopy in order to shed some light on annulate lamellae, primarily on their ultrastructural features, incidence, origin, fate and functional significance. No annulate lamellae were found in the nontumorous adenohypophyses and in 33 pituitary adenomas. They were, however, detected in two adenomas consisting of undifferentiated cells and one adenoma composed of sparsely granulated prolactin cells indicating that these unique membrane configurations cannot be regarded as an exceedingly rare finding and, furthermore, that they may be disclosed not only in undifferentiated but occasionally in highly differentiated cells. Annulate lamellae may arise from endoplasmic reticulum and/or nuclear envelope and consist of arrays of smooth walled double membrane sheets exhibiting regularly spaced interruptions as well as continuities with the endoplasmic reticulum. No relationship was established between annulate lamellae and adenohypophysial secretory activity. Our findings seem to be consistent with the view that annulate lamellae are present in those cells which have the tendency to proliferate.