1
|
Abstract
OBJECTIVES Acute pancreatitis (AP) is characterized by pancreatic microcirculatory and secretory disturbances. As galanin can modulate pancreatic vascular perfusion, we sought to determine if galanin plays a role in AP. METHODS Acute pancreatitis was induced in wild-type and galanin gene knockout mice by intraperitoneal injections of cerulein. The severity of AP was evaluated (plasma amylase and lipase, myeloperoxidase activity, and acinar cell necrosis) with and without treatment with galanin or the antagonist galantide. Galanin receptor messenger RNA expression in mouse pancreas was measured by reverse transcription-polymerase chain reaction and Western blot analysis. RESULTS Galantide ameliorated AP, reducing all indices by 25% to 40%, whereas galanin was without effect. In galanin knockout mice, all indices of AP were reduced 25% to 50% compared with wild-type littermates. Galanin administration to the knockout mice exacerbated AP such that it was comparable with the AP induced in the wild-type mice. Conversely, administration of galantide to the galanin knockout mice did not affect the AP, whereas AP was ameliorated in the wild-type mice. The 3 galanin receptor subtypes are expressed in mouse pancreas, with receptor subtype 3 expression predominating. CONCLUSIONS These data implicate a role for galanin in AP and suggest a potential clinical application for galanin antagonists in treatment.
Collapse
|
2
|
Abstract
As we know, the anterior pituitary is regulated by hypothalamic hormones via the portal system. However, our recent studies have demonstrated the presence of a substantial amount of substance P (SP)- and calcitonin gene-related peptide (CGRP)-containing nerve fibers in the anterior pituitary. In the present paper, the existence of a considerable amount of galanin (GAL)like immunoreactive (ir) nerve fibers with numerous of varicosities in the anterior pituitaries of the Macaca mulatta monkey and the dog were reported. In the monkey, GAL-ir nerve fibers with a large amount of varicosities were mainly located in the medial part of the gland, dominantly in its dorso-posterior regions. A great majority of varicosities were found to be closely related to the glandular tissue although some were located along the walls of blood sinus. GAL-ir nerve fibers were traced to enter the pars distalis of the anterior pituitary from the stalk as well as from the meningeal sheath covering the upper part of the anterior pituitary. Numerous GAL-ir cells presented in the pars distalis and the pars intermedia of the adenohypophysis. In the dog pituitary, GAL-ir nerve fibers were mainly located in the tail part and some in oral region. A majority of GAL-ir nerve fibers were at the periphery of the gland, especially in the medial planes, although some could be found deep in the gland. They appeared in individual fibers or in patches. Many GAL-ir nerve fibers and fiber fascicles existed in the median eminence and the sheath covering the tail and the oral part of the pituitary.
Collapse
Affiliation(s)
- Shaojun Liu
- Department of Neurobiology, Institute of Basic Medical Sciences, Academy of Military Medical Sciences, 27 Taiping Road, Beijing 100850, PR China
| |
Collapse
|
3
|
Freeman ME, Kanyicska B, Lerant A, Nagy G. Prolactin: structure, function, and regulation of secretion. Physiol Rev 2000; 80:1523-631. [PMID: 11015620 DOI: 10.1152/physrev.2000.80.4.1523] [Citation(s) in RCA: 1463] [Impact Index Per Article: 61.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Prolactin is a protein hormone of the anterior pituitary gland that was originally named for its ability to promote lactation in response to the suckling stimulus of hungry young mammals. We now know that prolactin is not as simple as originally described. Indeed, chemically, prolactin appears in a multiplicity of posttranslational forms ranging from size variants to chemical modifications such as phosphorylation or glycosylation. It is not only synthesized in the pituitary gland, as originally described, but also within the central nervous system, the immune system, the uterus and its associated tissues of conception, and even the mammary gland itself. Moreover, its biological actions are not limited solely to reproduction because it has been shown to control a variety of behaviors and even play a role in homeostasis. Prolactin-releasing stimuli not only include the nursing stimulus, but light, audition, olfaction, and stress can serve a stimulatory role. Finally, although it is well known that dopamine of hypothalamic origin provides inhibitory control over the secretion of prolactin, other factors within the brain, pituitary gland, and peripheral organs have been shown to inhibit or stimulate prolactin secretion as well. It is the purpose of this review to provide a comprehensive survey of our current understanding of prolactin's function and its regulation and to expose some of the controversies still existing.
Collapse
Affiliation(s)
- M E Freeman
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4340, USA.
| | | | | | | |
Collapse
|
4
|
Vacher P, Vacher AM, Mollard P. Tubocurarine blocks a calcium-dependent potassium current in rat tumoral pituitary cells. Mol Cell Endocrinol 1998; 139:131-42. [PMID: 9705081 DOI: 10.1016/s0303-7207(98)00066-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We investigated the effects of potassium channel inhibitors on electrical activity, membrane ionic currents, intracellular calcium concentration ([Ca2+]i) and hormone release in GH3/B6 cells (a line of pituitary origin). Patch-clamp recordings show a two-component after hyperpolarization (AHP) following each action potential (current clamp) or a two-component tail current (voltage-clamp). Both components can be blocked by inhibiting Ca2+ influx. Application of D-tubocurarine (dTc) (20-500 microM) reversibly suppressed the slowly decaying Ca2+-activated K+ tail current (I AHPs) in a concentration-dependent manner. On the other hand, low doses of tetraethylammonium ions (TEA+) only blocked the rapidly decaying voltage- and Ca2+-activated K+ tail current (I AHPf). Therefore, GH3/B6 cells exhibit at least two quite distinct Ca2+-dependent K+ currents, which differ in size, voltage- and Ca2+-sensitivity, kinetics and pharmacology. These two currents also play quite separate roles in shaping the action potential. d-tubocurarine increased spontaneous Ca2+ action potential firing, whereas TEA increased action potential duration. Thus, both agents stimulated Ca2+ entry. I AHPs is activated by a transient increase in [Ca2+]i such as a thyrotrophin releasing hormone-induced Ca2+ mobilization. All the K+ channel inhibitors we tested: TEA, apamin, dTC and charybdotoxin, stimulated prolactin and growth hormone release in GH3/B6 cells. Our results show that I AHPs is a good sensor for subplasmalemmal Ca2+ and that dTc is a good pharmacological tool for studying this current.
Collapse
Affiliation(s)
- P Vacher
- Laboratory of Neurophysiology, CNRS UMR 5543 University V. Segalen, Bordeaux, France
| | | | | |
Collapse
|
5
|
Liu S, Gao J. The relationship of galanin immunoreactive nerve fibers to glandular cells in the anterior pituitary in the monkey. Brain Res 1998; 781:114-20. [PMID: 9507082 DOI: 10.1016/s0006-8993(97)01227-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The anterior pituitary is known to be regulated by hypothalamic hormones via the portal system. However, our recent studies have demonstrated the presence of a substantial amount of substance P (SP)-, calcitonin gene-related peptide (CGRP)- and galanin (GAL)- immunoreactive (ir) nerve fibers with numerous varicosities in the anterior pituitaries of the Macaca mulatta monkey. The present study investigated the relationship of the GAL-ir nerve fibers to the glandular cells. The M. mulatta monkeys were used and sections of the anterior pituitary were double immunostained. GAL-ir nerve fibers and/or varicosities were found in proximity to contact directly with corticotropes, somatotropes, lactotropes, gonadotropes and thyrotropes without any exception. These findings indicate that a direct neural factor may be involved in the regulation of adenohypophyseal secretion.
Collapse
Affiliation(s)
- S Liu
- Department of Neurobiology, Institute of Neuroscience, The Fourth Military Medical University, Xian, China
| | | |
Collapse
|
6
|
Kask K, Berthold M, Bartfai T. Galanin receptors: involvement in feeding, pain, depression and Alzheimer's disease. Life Sci 1997; 60:1523-33. [PMID: 9126874 DOI: 10.1016/s0024-3205(96)00624-8] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Galanin, a neuroendocrine peptide with a multitude of functions, binds to and acts on specific G-protein coupled receptors. Only one galanin receptor subtype, GalRI, has been cloned so far, although pharmacological evidence suggests the presence of more than one galanin receptor subtype. These receptors mediate via different Gi/Go-proteins the inhibition of adenylyl cyclase, opening of K+-channels and closure of Ca2+-channels. Galanin inhibits secretion of insulin, acetylcholine, serotonin and noradrenaline, while it stimulates prolactin and growth hormone release. Determination of structural components of galanin receptors required for binding of the peptide ligand as carried out recently will facilitate the screening and design of molecules specifically acting on galaninergic systems with therapeutic potential in Alzheimer's disease, feeding disorders, pain and depression.
Collapse
Affiliation(s)
- K Kask
- Department of Neurochemistry and Neurotoxicology, Stockholm University, Sweden
| | | | | |
Collapse
|
7
|
Hyde JF, Moore JP, Drake KW, Morrison DG. Galanin gene expression in radiothyroidectomy-induced thyrotroph adenomas. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:E24-30. [PMID: 8760077 DOI: 10.1152/ajpendo.1996.271.1.e24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Galanin gene expression is markedly increased in the anterior pituitary glands of estrogen-treated rats (lactotroph hyperplasia) as well as human growth hormone-releasing hormone transgenic mice (somatotroph hyperplasia). The objective of this study was to examine galanin in a mouse model of thyrotroph adenoma formation. Male mice were radiothyroidectomized by use of iodine-131 (131I), and galanin peptide levels were assessed in the hypothalamic-pituitary axis. Immunoreactive galanin concentrations in the anterior pituitaries of 131I-treated mice were decreased 80% at 3, 6, 9, and 12 mo after radiothyroidectomy. Galanin peptide levels in the hypothalamus were decreased 20-25% at these times. Treatment with either estradiol or 3,3',5-triiodo-L-thyronine increased galanin peptide concentrations in the anterior pituitaries of 131I-treated mice, but neither treatment restored galanin concentrations. Galanin mRNA levels were decreased > 80% 1 yr after radiothyroidectomy. We conclude that, unlike animal models of lactotroph and somatotroph hyperplasia, galanin gene expression is suppressed throughout the development of thyrotroph adenomas, suggesting that galanin does not have a stimulatory role in the proliferation of thyrotrophs. Moreover, these data show that thyroid hormones are important positive regulators of galanin gene expression in the mouse and that estrogen may stimulate galanin gene expression in the absence of thyroid hormones.
Collapse
Affiliation(s)
- J F Hyde
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington 40536, USA.
| | | | | | | |
Collapse
|
8
|
Abstract
1. Galanin is a 29 (in humans 30) amino acids long neuropeptide with mostly inhibitory, hyperpolarizing actions. 2. Differential structural requirements of truncated forms of galanin and differential agonist/antagonist behaviour of chimeric peptides, high affinity galanin receptor ligands suggest the presence of pharmacologically distinct galanin receptor subtypes. 3. The galanin receptor from human Bowes melanoma cell line--a member of G-protein coupled receptor superfamily--has been cloned. 4. Galanin acts via Gi/G(o) proteins inhibiting cAMP production, inositol phosphate turnover, opening K+ channels or closing Ca2+ channels.
Collapse
Affiliation(s)
- K Kask
- Department of Neurochemistry and Neurotoxicology, Stockholm University, Sweden
| | | | | |
Collapse
|
9
|
Cytosolic Ca2+ of excitable pituitary cells at resting potentials is controlled by steady state Ca2+ currents sensitive to dihydropyridines. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31511-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
10
|
Giustina A, Bonfanti C, Licini M, De Rango C, Milani G. Inhibitory effect of galanin on growth hormone release from rat pituitary tumor cells (GH1) in culture. Life Sci 1994; 55:1845-51. [PMID: 7526106 DOI: 10.1016/0024-3205(94)90095-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The growth hormone (GH) releasing effect of GH-releasing hormone (GHRH) and galanin, a 29-amino acid peptide widely distributed in mammalian CNS, was investigated in cultured rat pituitary tumor cells (GH1) as compared to normal rat somatotrophs. GHRH stimulated dose-dependently GH secretion in normal somatotrophs but did not affect GH secretion in GH1 cells. Galanin (1-10 microM) stimulated GH release in a concentration-dependent manner, but with lower potency as compared to GHRH, in normal rat pituitaries but was inhibitory in rat GH1 cells. The results of this study indicate that while galanin has the ability to stimulate GH release from dispersed pituitary cells of normal rats it has potent direct inhibitory effects on GH release from tumor rat cells.
Collapse
Affiliation(s)
- A Giustina
- Sezione di Endocrinologia, School of Medicine, University of Brescia, Italy
| | | | | | | | | |
Collapse
|
11
|
Guérineau NC, Bouali-Benazzouz R, Corcuff JB, Audy MC, Bonnin M, Mollard P. Transient but not oscillating component of the calcium mobilizing response to gonadotropin-releasing hormone depends on calcium influx in pituitary gonadotrophs. Cell Calcium 1992; 13:521-9. [PMID: 1423532 DOI: 10.1016/0143-4160(92)90020-s] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Gonadotropin-releasing hormone (GnRH)-stimulated changes in the cytosolic free Ca2+ concentration ([Ca2+]i) were studied in gonadotrophs cultured from 3-week ovariectomized rat pituitaries. One animal was used per cell preparation. [Ca2+]i was monitored in individual gonadotrophs by dual emission microspectrofluorimetry, using Indo-1 as the intracellular fluorescent Ca2+ probe. A short stimulation with GnRH evoked a complex concentration-dependent Ca2+ response in individual gonadotrophs. 0.1-1 nM GnRH triggered a series of sinusoidal-like [Ca2+]i oscillations superimposed upon a modest slow [Ca2+]i rise--the oscillating response mode--while 10-100 nM GnRH caused a biphasic increase in [Ca2+]i consisting of a monophasic transient and oscillations--the transient/oscillating response mode. Despite the consistency of Ca2+ responses, an inter-preparation heterogeneity of [Ca2+]i oscillations frequency was noticed. Moreover, we observed that, within a given cell preparation, the frequency of [Ca2+]i oscillations was independent of GnRH concentration whereas both peak [Ca2+]i and area under the [Ca2+]i versus time curve were concentration-dependent. Thus, in gonadotrophs, the presence of the GnRH signal would lead to [Ca2+]i oscillations, while the amplitude of the [Ca2+]i responses would code for the concentration of agonist. Both transient and oscillating components of GnRH responses depended on releasing activity of Ca(2+)-sequestering pools in as much as GnRH responses were unaffected by brief removal of external Ca2+, but suppressed by chelating intracellular free Ca2+ with BAPTA. However, prolonged exposure to a Ca(2+)-free medium suppressed the transient component while leaving the oscillating component unaffected. We therefore propose that gonadotrophs employ Ca(2+)-sequestering pools, whose maintenance depends on a slow Ca(2+)-entry, to give an amplitude-coded Ca2+ rise in response to a short GnRH stimulation.
Collapse
Affiliation(s)
- N C Guérineau
- Laboratory of Neurophysiology, CNRS URA 1200, University of Bordeaux, France
| | | | | | | | | | | |
Collapse
|