open access

Vol 56, No 6 (2005)
Original papers
Published online: 2006-06-26
Submitted: 2013-02-15
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Effect of monthly administration of GHRH (fragment 1-29) with osmotic pump on the rat anterior pituitary

Ewelina Motylewska, Gabriela Mełeń-Mucha, Sławomir Mucha, Marek Pawlikowski
Endokrynologia Polska 2005;56(6):927-932.

open access

Vol 56, No 6 (2005)
Original papers
Published online: 2006-06-26
Submitted: 2013-02-15

Abstract

Growth Hormone-Releasing Hormone (GHRH) is the main factor, which regulates GH secretion and somatotrope proliferation. However, its chronic effect on anterior pituitary gland is still unknown. It is known that excessive GHRH secretion in patients with gastroenteropancreatic tumors secreting GHRH results in acromegaly and somatotrope hyperplasia. In mice transgenic for GHRH somatotrope tumors develop. Thus, the aim of this paper was to examine the effect of GHRH chronic administration on somatotrope secretion, their percentage and cell proliferation in anterior pituitary gland in rats. The experiment was performed on male Fischer 344 rats weighing 200 ± 20 g. The animals were divided into two groups: group I – controls (13 rats) received solvent for GHRH (5% ethanol in demineralized water); group II (10 rats) received GHRH (Growth Hormone Releasing Factor, fragment 1-29 amide) at a dose of 5 µg/day. The substances were given for 1 month via osmotic pump (ALZET), which were implanted subcutaneously in the dorsal region under ketamin anesthesia. After 4 weeks all rats were decapitated and the blood was collected. In the microscopic preparations of anterior pituitary gland the morphology of pituitary (Herlant staining) and the percentage of somatotrope cells and proliferation index based on PCNA staining were assessed. It was found that the chronic treatment with GHRH caused a statistically significant increase in serum rGH concentration and in percentage of somatotropes, but did not change proliferation index and did not induce pathological changes in the morphology of the anterior pituitary gland when compared to the control group. Summing up, monthly GHRH administration did not induce somatotrope adenomas but it caused serum GH level elevation, what seems to depend partially on the increase of somatotrope number.

Abstract

Growth Hormone-Releasing Hormone (GHRH) is the main factor, which regulates GH secretion and somatotrope proliferation. However, its chronic effect on anterior pituitary gland is still unknown. It is known that excessive GHRH secretion in patients with gastroenteropancreatic tumors secreting GHRH results in acromegaly and somatotrope hyperplasia. In mice transgenic for GHRH somatotrope tumors develop. Thus, the aim of this paper was to examine the effect of GHRH chronic administration on somatotrope secretion, their percentage and cell proliferation in anterior pituitary gland in rats. The experiment was performed on male Fischer 344 rats weighing 200 ± 20 g. The animals were divided into two groups: group I – controls (13 rats) received solvent for GHRH (5% ethanol in demineralized water); group II (10 rats) received GHRH (Growth Hormone Releasing Factor, fragment 1-29 amide) at a dose of 5 µg/day. The substances were given for 1 month via osmotic pump (ALZET), which were implanted subcutaneously in the dorsal region under ketamin anesthesia. After 4 weeks all rats were decapitated and the blood was collected. In the microscopic preparations of anterior pituitary gland the morphology of pituitary (Herlant staining) and the percentage of somatotrope cells and proliferation index based on PCNA staining were assessed. It was found that the chronic treatment with GHRH caused a statistically significant increase in serum rGH concentration and in percentage of somatotropes, but did not change proliferation index and did not induce pathological changes in the morphology of the anterior pituitary gland when compared to the control group. Summing up, monthly GHRH administration did not induce somatotrope adenomas but it caused serum GH level elevation, what seems to depend partially on the increase of somatotrope number.
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Keywords

pituitary gland; proliferation; somatorelin; somatotrope

About this article
Title

Effect of monthly administration of GHRH (fragment 1-29) with osmotic pump on the rat anterior pituitary

Journal

Endokrynologia Polska

Issue

Vol 56, No 6 (2005)

Pages

927-932

Published online

2006-06-26

Bibliographic record

Endokrynologia Polska 2005;56(6):927-932.

Keywords

pituitary gland
proliferation
somatorelin
somatotrope

Authors

Ewelina Motylewska
Gabriela Mełeń-Mucha
Sławomir Mucha
Marek Pawlikowski

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