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Journal Article 2007; 28(4): 382-385 PubMed PMID: 17693986 Citation  Keywords:  Animals, Biological Assay:methods, Cells, Cultured, Dose-Response Relationship, Drug, Enzyme Stability:physiology, Growth Hormone:metabolism, Growth Hormone-Releasing Hormone:analogs & derivatives, Male, Pituitary Gland:cytology, Rats, Rats, Inbred WKY,.   

OBJECTIVE: It has been found that hGH-RH analogues with increased resistance to enzymatic degradation have a much higher potency than the native hGH-RH (1-29)-NH2 and have an ability to partially reverse growth hormone deficiencies.

THE AIM: The aim of these studies was to elaborate a method which can be used for preliminary evaluation of new GH-RH analogues both from the point of view of their potency to release GH and enzymatic stability.

METHOD: Two highly active GH-RH analogues with increased resistance to trypsin-like enzymes, and hGH-RH(1-29)-NH2 used as a standard, in doses 1 nM, 10 nM, and 100 nM were added to pituitary rat cell culture, and medium was collected after 30, 60, 120 and 240 min. GH concentration was measured by RIA kit.

RESULTS: It was observed that the potency of these two GH-RH analogues was several times higher than that of native compound. Moreover, the stimulation was much longer. This suggests that high activity of these analogues in vivo could be the result of increased enzymatic stability.

CONCLUSION: This method can be used for selecting more potent and more stable releasing peptides before in vivo evaluation....

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Comparative Study 2007; 28(2): 166-169 PubMed PMID: 17435668 Citation  Keywords:  Adiponectin:blood, Animals, Inflammation:chemically induced, Injections, Intraperitoneal, Lipopolysaccharides, Male, Pituitary Adenylate Cyclase-Activating Polypeptide:administration & dosage, Rats, Rats, Inbred WKY,.   

BACKGROUND: Pituitary adenylate cyclase activating peptide (PACAP 38) is a neuropeptide with anti-inflammatory activity. Vasoactive intestinal peptide (VIP)/PACAP receptors are found in immune cells, endocrine glands and also in adipose tissue. Adiponectin is an adipocyte-derived protein hormone which possesses anti-inflammatory, antidiabetic and antiatherogenic properties. The aim of this study was to examine the influence of PACAP 38 on adiponectin release in basal conditions and during lipopolysaccharide (LPS)-induced acute inflammation.

METHODS: Male Wistar-Kyoto rats were divided into four groups which received intraperitoneal injections of 0.9% NaCl, LPS, PACAP 38 or LPS+PACAP 38, respectively. Serum adiponectin concentrations were measured using an ELISA test.

RESULTS: LPS administration did not change adiponectin concentration; however, PACAP 38 administered alone decreased serum adiponectin concentration after 2 h (p<0.05) and 4 h (p<0.01). In the group that received LPS+PACAP38, compared with LPS alone, no difference in adiponectin concentration was observed.

CONCLUSIONS: We conclude that PACAP 38 may directly modulate adiponectin secretion by adipocytes in basal conditions....

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Journal Article 2006; 27(1-2): 257-259 PubMed PMID: 16648808 Citation  Keywords:  Animals, Bombesin:pharmacology, Estradiol:pharmacology, Estrogens:pharmacology, Female, Injections, Intraventricular, Luteinizing Hormone:antagonists & inhibitors, Ovariectomy, Rats, Rats, Inbred WKY,.   

OBJECTIVE: Bombesin, 14-amino acid peptide, discovered in the gastrointestinal tract, is widely distributed in the central nervous system (CNS). The specific receptors of bombesin in the pituitary have been characterized. Bombesin plays an important role in the gastric and pancreatic secretion, in the mechanism of food intake, thermoregulation and in pituitary hormone secretion. There are contentious opinions about the effect of bombesin on hormone secretion.

THE AIM: The aim of this study was to evaluate the effect of estrogens in the modulation of bombesin action on LH release.

RESEARCH METHODS: Female Wistar-Kyoto rats, two weeks after ovariectomy (OVX), were implanted with a cannula being located in the third cerebroventricle. Thereafter, the rats were primed with 17beta estradiol in a dose of 25microg/0.2ml s.c. for three consecutive days. On the day of the experiment, bombesin at a concentration of 0.5 microg in 5microl vehicle (artificial cerebrospinal fluid) or equal volume of the vehicle was infused into the third ventricle with an automatic pump. At 60 or 120 min after the infusion the animals were decapitated, and the trunk blood was collected. Rat serum LH was measured by RIA kit supplied by Dr A.F. Parlow from NIDDK Baltimore, MD.

RESULTS: Bombesin inhibited LH release at 120 min and it did not change LH release at 60 min after icv administration.

CONCLUSIONS: The response of LH release after central injection of bombesin is modified by estrogens....

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Journal Article 2006; 27(1-2): 153-156 PubMed PMID: 16648801 Citation  Keywords:  Animals, Cells, Cultured, Dose-Response Relationship, Drug, Growth Hormone:metabolism, Male, Neuropeptides:pharmacology, Pituitary Gland:cytology, Radioimmunoassay, Rats, Rats, Inbred WKY,.   

OBJECTIVE: Cortistatin (CST) is a 17-amino acid neuropeptide expressed mainly in the cortex and hippocampus. It is also found in the peripheral tissues such as the stomach, kidney, pancreas and the immune system. Two forms of cortistatin CST-17, CST-29 bind with high affinity all somatostatin (SS) receptor subtypes. It has been reported that a receptor called MrgX(2) is able to selectively bind both CST-17 and CST-14 rather than SS. In human tissues CST-17 and CST-29, rather than SS, also bind ghrelin receptor GHS-r1a. In in vivo experiments CST inhibited GH and insulin secretion.

THE AIM: The aim of this study was to evaluate the effect of cortistatin on GH release in in vitro experiments.

RESEARCH METHODS: CST-14 and SS-14 in doses of 1nMol, 10nMol, and 100nMol were added after 48 hrs of pituitary cell culture, and the medium was collected 30, 60, 120, 240 min thereafter. rGH was measured with RIA kits provided by Linco.

RESULTS: CST-14 stimulated GH release from cultured pituitary cells in a dose dependent manner. The maximum effect of CST-14 was observed after 60 min of incubation. However, SS-14 in doses of 10 nMol and 100 nMol inhibited GH release.

CONCLUSION: A direct stimulating effect of Cortistatin-14 on GH release from cultured pituitary cells was found....

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Journal Article 2006; 27(1-2): 60-62 PubMed PMID: 16648774 Citation  Keywords:  Adrenocorticotropic Hormone:blood, Animals, Corticosterone:blood, Growth Hormone:blood, Injections, Intraventricular, Male, Nerve Tissue Proteins:pharmacology, Pituitary-Adrenal System:drug effects, Prolactin:blood, Rats, Rats, Inbred WKY,.   

OBJECTIVE: It has been reported that the cocaine and amphetamine regulated transcript (CART) is widely expressed in the hypothalamic nuclei involved in the mechanism of hormonal secretion.

RESEARCH METHODS: In order to evaluate the effect of CART on the activation of the pituitary-adrenal axis in the rat, CART (55-102) in a dose of 0.5 microg in 5 microl CSF was infused into the third ventricle (icv) with an automatic pump. At 10, 30, 60, 120 min after the infusion of CART or vehicle, the animals were decapitated and the trunk blood was collected. Serum ACTH and corticosterone concentrations were measured with RIA kits provided by Phoenix Pharmaceuticals and ICN Biomedicals USA, respectively.

RESULTS: The stimulating effect of CART on ACTH concentration was observed only 30 min after icv injection. However, CART stimulated corticosterone release at 10, 30, 60 min after icv injection.

CONCLUSIONS: CART (55-102) administered intracerebroventricularly (icv) stimulated ACTH and corticosterone release. The stimulating effect of CART on ACTH was short-lived....

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Comparative Study 2005; 26(6): 680-684 PubMed PMID: 16380707 Citation  Keywords:  Amyloid:administration & dosage, Animals, Cells, Cultured, Dose-Response Relationship, Drug, Injections, Intravenous, Injections, Intraventricular, Islet Amyloid Polypeptide, Male, Pituitary Gland:cytology, Prolactin:blood, Rats, Rats, Inbred WKY,.   

OBJECTIVE: Amylin is a 37-amino acid peptide that is secreted from the pancreatic beta cells. This peptide is cosecreted with insulin from the pancreas by glucose. Amylin plays a role in glucose homeostasis and in the regulation of lipid metabolism. Amylin receptors were identified in central nervous system of rats. There is no available data on the effects of amylin on the pituitary hormones secretion. The aim of this study was to evaluate the effect of amylin on prolactin release in vivo and in vitro experiments in male adult Wistar Kyoto rats.

METHODS: Amylin in a dose of 1 microg/5 microl was injected intraventricularly (i.c.v) during 5 min. using automatic pump. The control group received 5 microl cerebrospinal fluid. Amylin was injected intravenously (i.v) in a dose of 10 microg in 300 microl 0.9% NaCl. The control group received 300 microl 0.9% NaCl. In vitro experiment was performed in the pituitary cells culture conditions. Amylin was added to pituitary cell culture in a dose of 1, 10, 100 nM. Prolactin concentrations were determined using RIA methods.

RESULTS: Central or peripheral administration of amylin caused a significant decrease of serum PRL concentrations as compared with control after 120 min. After 240 minute incubation of the pituitary cells culture with amylin in doses of 10 nM and 100 nM a significant inhibition of the release of PRL was found. However we found that the effect of amylin on the release of PRL depended on dose and time of incubation. A significant increase of PRL level was observed in cultured media in the presence of 1 nM of amylin after 60 min.

CONCLUSION: Our results indicate that amylin administrated centrally and peripherally as well in the cell culture inhibits PRL release....

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Comparative Study 2005; 26(5): 468-472 PubMed PMID: 16264417 Citation  Keywords:  Animals, Cells, Cultured, Female, Galanin:administration & dosage, Injections, Intravenous, Injections, Intraventricular, Ovariectomy, Pituitary Gland:drug effects, Pituitary Hormones:blood, Rats, Rats, Inbred WKY,.   

OBJECTIVES: Galanin and its receptors are widely distributed within the central and peripheral nervous system, especially in hypothalamus including preoptic area, paraventricular nucleus (PVN), supraoptic nucleus (SON) and median eminence. Galanin plays an important role in the control of food intake, energy expenditure, reproduction, water balance and various neuroendocrine functions. Galanin may affect hormones release, but the exact mechanism of the peptide action remains unclear and possible direct effects of galanin on the pituitary are controversial. The aim of this study was to examine the effects of galanin on pituitary hormones release after the central and peripheral administration of the peptide.

MATERIAL AND METHODS: (i) Experiment I - Intracerebroventricular (icv) administration of galanin: Galanin at a concentration of 0.5 microg in 5microl vehicle (artificial cerebrospinal fluid) or equal volume of the vehicle was slowly (1microl/min) infused into the third ventricle with an automatic pump (CMA/100; Sweden) through an inner cannula inserted into the guide cannula. After the end of the infusion the rats were transferred to their home cages with free access to food and water. At 60 min after the infusion of galanin or vehicle, animals were decapitated and trunk blood was collected in plastic tubes containing 1000 IU aprotinin (inhibitor of protease) per each ml of blood. (ii) Experiment II - Intravenous (iv) injection of galanin: Galanin in a dose of 10 microg in 300 microl of saline or 300 microl of saline alone was injected into the tail vein. After the injection the animals were transferred to individual cages with free access to food and water. At 60 min after the injection of galanin or saline, animals were decapitated, and trunk blood was collected in plastic tubes containing 1000 IU of aprotinin (Trascolan). The blood samples were centrifuged (3000 rpm for 20 min at 4 degrees C). Serum samples were frozen until hormonal analyses were performed. Serum rLH, rFSH, rPRL, rGH, rTSH concentrations were measured with RIA methods.

RESULTS: Galanin administered icv increased significantly rPRL and rTSH levels (p<0.01, p<0.05, respectively). Plasma rPRL and rTSH concentrations were not changed after iv injection of galanin. Galanin injected centrally inhibited significantly rGH release (p<0.01), however, galanin given iv stimulated rGH (p<0.01). Serum rLH and rFSH concentrations were not changed after icv and iv injections of galanin.

CONCLUSION: Galanin may be involved in the modulating mechanism of pituitary hormones release....

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Comparative Study 2005; 26(5): 459-462 PubMed PMID: 16264390 Citation  Keywords:  Animals, Female, Injections, Intravenous, Injections, Intraventricular, Leptin:administration & dosage, Ovariectomy, Pituitary Hormones:blood, Radioimmunoassay, Rats, Rats, Inbred WKY,.   

OBJECTIVE: It has been reported that leptin plays an important role in the regulation of food intake and energy expenditure. There are controversial opinions about effects of leptin on the hormonal system. The aim of this study was to estimate the effect of leptin on pituitary hormones release after central and peripheral administration.

METHODS: Leptin was injected intracerebroventricularly (icv) in a dose of 0.5 microg/5microl aCSF (artificial cerebrospinal fluid) for 5 min in Wistar Kyoto rats. At 60 and 120 min after injections the animals were decapitated. Leptin in a dose of 10 microg in 300 microl of saline was administered intravenously (i.v). At 60 mins the animals were decapitated. Serum rLH, rFSH, rPRL, rTSH, rGH concentrations were measured with RIA methods.

RESULTS: After central (icv) injection of leptin we observed an increase of rGH, rTSH and a decrease of rPRL. However, after peripheral (iv) injection of leptin we found a decrease of rGH and rTSH and an increase of rPRL. We did not find any significant changes in LH and FSH after icv and iv injection of leptin.

CONCLUSIONS: The opposite effects of leptin on pituitary hormones release were observed due to the method of leptin administration. Leptin may play a modulating role in the mechanism of pituitary hormones release....

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