Search NEL Online

Journal Article 2011; 32(1): 96-101 PubMed PMID: 21407161 Citation  Keywords:  Adenoma:metabolism, Adult, Aged, Biopsy, Female, Gonadotropins, Pituitary:metabolism, Humans, Male, Middle Aged, Neoplasm Recurrence, Local:metabolism, Pituitary Neoplasms:metabolism, Receptors, Somatostatin:metabolism,.   

OBJECTIVE: Surgical treatment of pituitary macroadenomas often fails because of tumor recurrence after the operation. The causes of tumor recurrence are complex, but one of them may be the high growth potential of the adenoma. As somatostatin receptors mediate antiproliferative, anti-angiogenic and pro-apoptotic actions, it seemed reasonable to investigate their expression in dependence on the adenoma recurrence.

METHODS: Samples of primary and recurrent gonadotropinomas excised surgically from patients were examined. This type of pituitary adenomas was chosen because of its relatively high recurrence rate. The adenoma phenotype and expression of somatostatin receptor subtypes 1-5 (SSTR 1-5) were investigated by immunohistochemistry, and the level of SSTR expression was semiquantitatively scored.

RESULTS: It was found that the adenomas undergoing the early recurrence have lower expression of SSTR 2A and 3 in comparison to those which did not recur during 5 years lasting observation. On the other hand, the recurrent tumors show higher expression of SSTR 1, 2A, 3 and 5 subtypes than their primary counterparts.

CONCLUSIONS: It is hypothesized that SSTR may, at least in part, counteract adenoma recurrence. On the other hand, it can be also presumed that the recurrent gonadotropinomas may be more sensitive to somatostatin analog treatment than primary ones. These hypotheses need to be confirmed in further studies....

Read abstract  Full text PDF

Journal Article 2008; 29(1): 113-116 PubMed PMID: 18283262 Citation  Keywords:  Adenoma:metabolism, Adult, Aged, Female, Growth Hormone:metabolism, Hemangiopericytoma:metabolism, Humans, Male, Middle Aged, Pituitary Neoplasms:metabolism, Prolactin:metabolism, Receptors, Somatostatin:metabolism, Somatostatin:pharmacology, Tumor Cells,.   

OBJECTIVES: The aim of the study was to examine the effect of somatostatin (SST) on vascular endothelial growth factor (VEGF) secretion from clinically non-functioning pituitary tumors incubated in vitro.

MATERIAL AND METHODS: Eight pituitary tumors surgically removed were investigated. All of the tumors were diagnosed before surgery as non-functioning. Seven of them were diagnosed after surgery as pituitary adenomas and expressed either gonadotropins or their subunits as detected by immunohistochemistry. Two tumors additionally expressed prolactin and growth hormone. One tumor was immunonegative for pituitary hormones and was diagnosed as haemangiopericytoma. All tumors but one were investigated immunohistochemically to detect the somatostatin receptors and expressed at least 3 of 5 subtypes of somatostatin receptors. The cells isolated from the examined tumors were exposed in vitro to native SST-14. The concentration of VEGF in the culture media was performed by means of ELISA method.

RESULTS: It was found that the exposure on SST-14 resulted in the divergent changes (increase in 4 cases and decrease in 3 cases) in VEGF concentrations in the medium. It seems that the inhibition of VEGF secretion is related to the expression of somatostatin receptor subtypes sst1 and sst2.

CONCLUSIONS: The response of VEGF secretion from pituitary tumoral cells to SST seems to depend on the spectrum of expressed somatostatin receptor subtypes. However, this presumption needs further studies on the larger material....

Read abstract  Full text PDF

Journal Article 2006; 27(1-2): 169-173 PubMed PMID: 16648773 Citation  Keywords:  Actins:metabolism, Adenoma:metabolism, DNA, Complementary:biosynthesis, Ghrelin, Glyceraldehyde-3-Phosphate Dehydrogenases:metabolism, Human Growth Hormone:metabolism, Humans, Peptide Hormones:biosynthesis, Pituitary Neoplasms:metabolism, RNA, Messenger:b.   

: Ghrelin is one of the peptides involved into GH-release, binding to specific GHS receptors on hypothalamus and pituitary. The ghrelin peptide and ghrelin mRNA have been detected in several regions of hypothalamus, in normal pituitary, as well as in various types of pituitary adenoma, with different levels of expression in different tumour types. We decided to determine the expression of ghrelin in somatotroph adenomas. Human pituitary somatotroph adenoma tissues were obtained at the time of transsphenoidal surgery from 3 acromegalic patients and studied for ghrelin mRNA expression. Before surgery each patient received a somatostatin analogue treatment at doses 20 mg, 30 mg, 30 mg at 30 days intervals. 20 mg of each tissue sample was used for the isolation of total cellular RNA. The reverse transcription and real-time PCR were performed according to Korbonits et al. method. The reverse transcription of total RNA to cDNA was performed using Super Script TM Rnase H RT kit according to manufacturer protocol. We wished to determine the number of copies of ghrelin gene within the single cell. We used the beta-actin, and the GAPDH genes as a reference molecules for standard curve calculation. Ghrelin mRNA was not detected in any examined tissues. We postulate that the absence of the ghrelin gene transcript is mainly due to the treatment with somatostatin analogues administered preoperatively, which could have suppressed the ghrelin gene transcription....

Read abstract