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Frutos MGS, Cacicedo L, Fernández C, Vicent D, Velasco B, Zapatero H, Sánchez-Franco F. Insights into a role of GH secretagogues in reversing the age-related decline in the GH/IGF-I axis. Am J Physiol Endocrinol Metab 2007; 293:E1140-52. [PMID: 17684105 DOI: 10.1152/ajpendo.00236.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Growth hormone (GH) secretion and serum insulin-like growth factor-I (IGF-I) decline with aging. This study addresses the role played by the hypothalamic regulators in the aging GH decline and investigates the mechanisms through which growth hormone secretagogues (GHS) activate GH secretion in the aging rats. Two groups of male Wistar rats were studied: young-adult (3 mo) and old (24 mo). Hypothalamic growth hormone-releasing hormone (GHRH) mRNA and immunoreactive (IR) GHRH dramatically decreased (P < 0.01 and P < 0.001) in the old rats, as did median eminence IR-GHRH. Decreases of hypothalamic IR-somatostatin (SS; P < 0.001) and SS mRNA (P < 0.01), and median eminence IR-SS were found in old rats as were GHS receptor and IGF-I mRNA (P < 0.01 and P < 0.05). Hypothalamic IGF-I receptor mRNA and protein were unmodified. Both young and old pituitary cells, cultured alone or cocultured with fetal hypothalamic cells, responded to ghrelin. Only in the presence of fetal hypothalamic cells did ghrelin elevate the age-related decrease of GH secretion to within normal adult range. In old rats, growth hormone-releasing peptide-6 returned the levels of GH and IGF-I secretion and liver IGF-I mRNA, and partially restored the lower pituitary IR-GH and GH mRNA levels to those of young untreated rats. These results suggest that the aging GH decline may result from decreased GHRH function rather than from increased SS action. The reduction of hypothalamic GHS-R gene expression might impair the action of ghrelin on GH release. The role of IGF-I is not altered. The aging GH/IGF-I axis decline could be rejuvenated by GHS treatment.
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Frutos MGS, Cacicedo L, Méndez CF, Vicent D, González M, Sánchez-Franco F. Pituitary alterations involved in the decline of growth hormone gene expression in the pituitary of aging rats. J Gerontol A Biol Sci Med Sci 2007; 62:585-97. [PMID: 17595414 DOI: 10.1093/gerona/62.6.585] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Growth hormone (GH) declines during aging. This study investigates whether pituitary constitutive alterations may be involved in the GH decline. Two groups of male Wistar rats were studied (young: 3-month-old; old: 24-month-old). The old rats showed lower pituitary GH messenger RNA (mRNA) levels, immunoreactive rat (IR)-GH content, and GH secretion with no difference in pituitary Pit-1 and cAMP-response element-binding protein (CREB) expression. Pituitary GH releasing hormone receptor (GHRH-R), GH secretagogue receptor (GHS-R), sstr2, and sstr5 mRNA levels were significantly reduced in old rats. The percentage of GH immunoreactive cells was similar in both groups. In vitro, pituitary IR-GH response to GHRH, forskolin (FK), ghrelin, and insulin-like growth factor I (IGF-I) was similar when compared with respective basal secretion and somatostatin-diminished GHRH- and ghrelin-induced IR-GH release in both groups. These results indicate that, as somatotrope function is maintained in aging, the changes observed in GH gene expression and secretion could be reversed by GHS.
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Affiliation(s)
- Miriam G San Frutos
- Endocrine Service, Hospital Carlos III, C/ Sinesio Delgado, 10, Madrid, Spain
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Perry SF, Gilmour KM, Vulesevic B, McNeill B, Chew SF, Ip YK. Circulating Catecholamines and Cardiorespiratory Responses in Hypoxic Lungfish (Protopterus dolloi): A Comparison of Aquatic and Aerial Hypoxia. Physiol Biochem Zool 2005; 78:325-34. [PMID: 15887079 DOI: 10.1086/430041] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2004] [Indexed: 11/03/2022]
Abstract
Circulating catecholamine levels and a variety of cardiorespiratory variables were monitored in cannulated bimodally breathing African lungfish (Protopterus dolloi) exposed to aquatic or aerial hypoxia. Owing to the purported absence of external branchial chemoreceptors in lungfish and the minor role played by the gill in O2 uptake, it was hypothesized that plasma catecholamine levels would increase only during exposure of fish to aerial hypoxia. The rapid induction of aquatic hypoxia (final PWo2 = 25.9+/-1.6 mmHg) did not affect the levels of adrenaline (A) or noradrenaline (NA) within the plasma. Similarly, none of the measured cardiorespiratory variables--including heart rate (fH), blood pressure, air-breathing frequency (fV), O2 consumption (Mo2), CO2 excretion (Mco2), or blood gases--were influenced by acute aquatic hypoxia. In contrast, however, the rapid induction of aerial hypoxia (inspired Po2=46.6+/-3.3 mmHg) caused a marked increase in the circulating levels of A (from 7.9+/-2.0 to 18.8+/-6.1 nmol L(-1)) and NA (from 7.7+/-2.2 to 19.7+/-6.3 nmol L(-1)) that was accompanied by significant decreases in Mo2, arterial Po2 (Pao2), and arterial O2 concentration (Cao2). Air-breathing frequency was increased (by approximately five breaths per hour) during aerial hypoxia and presumably contributed to the observed doubling of pulmonary Mco2 (from 0.25+/-0.04 to 0.49+/-0.07 mmol kg(-1) h(-1)); fH and blood pressure were unaffected by aerial hypoxia. An in situ perfused heart preparation was used to test the possibility that catecholamine secretion from cardiac chromaffin cells was being activated by a direct localized effect of hypoxia. Catecholamine secretion from the chromaffin cells of the heart, while clearly responsive to a depolarizing concentration of KCl (60 mmol L(-1)), was unaffected by the O2 status of the perfusion fluid. The results of this study demonstrate that P. dolloi is able to mobilize stored catecholamines and increase f(V) during exposure to aerial hypoxia while remaining unresponsive to aquatic hypoxia. Thus, unlike in exclusively water-breathing teleosts, P. dolloi would appear to rely solely on internal/airway O2 chemoreceptors for initiating catecholamine secretion and cardiorespiratory responses.
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Affiliation(s)
- S F Perry
- Department of Biology, University of Ottawa, 140 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada.
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Solomon MB. Effect of animal production on meat quality. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 542:1-23. [PMID: 15174569 DOI: 10.1007/978-1-4419-9090-7_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Bhatnagar M. Distribution of somatostatin (SS) immunoreactivity using specific rabbit antibodies in preoptic-anterior hypothalamus (PO-AH) of female rat brain. Brain Res 2001; 900:295-305. [PMID: 11334810 DOI: 10.1016/s0006-8993(00)03164-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Distribution of somatostatin (SS) immunoreactivity was observed in the preoptic-anterior hypothalamus (PO-AH) of the female rat brain. Six specific rabbit antibodies A (SS-14), B (SS-28), C (SS-28 complete), D (SS 14 and SS-28 both), E (SS preprohormone) and F (GHRH) were used for immunostaining using Avidin-Biotin Complex (ABC) method (Hsu et al., 1981). Immunostaining was observed with all the six antibodies, in the serial sections passing through various bregma levels (-0.3 to -3.3 mm) of preoptic-anterior hypothalamic (PO-AH) region including median eminence (ME). In conclusion, the present study suggests that immunoreactive nerve terminals for both SS-14 and SS-28 are present in internal (IZ) and external zones (EZ) of ME. High intensity of SS-14 and SS-28 containing terminals in EZ suggests that both SS fractions are involved in regulating GH secretion in anterior pituitary. This is a first report on comparative distribution of immunoreactivities of four different fractions of SS, SS-preprohormone and GHRH in PO-AH.
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Affiliation(s)
- M Bhatnagar
- Department of Zoology, University College of Science, M.L.S. University, 313001, Udaipur, India.
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Selmer I, Schindler M, Allen JP, Humphrey PP, Emson PC. Advances in understanding neuronal somatostatin receptors. REGULATORY PEPTIDES 2000; 90:1-18. [PMID: 10828487 DOI: 10.1016/s0167-0115(00)00108-7] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It has long been considered that somatostatin acts as a neuromodulator in the mammalian central nervous system but its precise physiological roles remain elusive. Early studies to identify somatostatin-binding sites revealed a widespread heterogeneous pattern, especially in the CNS. More recently, a family of somatostatin receptors have been identified, of which five genes (sst(1-5)) have been cloned. In this review, we discuss current data describing the localisation of the five receptor types. Recent progress in understanding their function has been made using high-affinity, selective receptor ligands and transgenic animal technology. Finally, the therapeutic potential for somatostatin receptor-selective compounds as analgesics is considered.
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Affiliation(s)
- I Selmer
- Department of Neurobiology, The Babraham Institute, Babraham Hall, CB2 4EF, Cambridge, UK.
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Interrelationships between somatostatin sst2A receptors and somatostatin-containing axons in rat brain: evidence for regulation of cell surface receptors by endogenous somatostatin. J Neurosci 1998. [PMID: 9437026 DOI: 10.1523/jneurosci.18-03-01056.1998] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Using an antipeptide antibody, we reported previously on the distribution of the somatostatin sst2A receptor subtype in rat brain. Depending on the region, immunolabeled receptors were either confined to neuronal perikarya and dendrites or distributed diffusely in tissue. To investigate the functional significance of these distribution patterns, we examined the regional and cellular relationships between somatostatin axons and sst2A receptors in the rat CNS, using double-labeling immunocytochemistry. Light and confocal microscopy revealed a significant correlation (p < 0.02) between the distribution of somatodendritic sst2A receptor immunoreactivity and that of somatostatin terminal fields, both quantitatively and qualitatively. Furthermore, in regions of somatodendritic labeling, a subpopulation of sst2A-immunoreactive cells was also immunopositive for somatostatin, suggesting that a subset of sst2A receptors consists of autoreceptors. By contrast, in regions displaying diffuse sst2A labeling only moderate to low densities of somatostatin terminals were observed, and no significant relationship was found between terminal density and receptor immunoreactivity. At the electron microscopic level, areas expressing somatodendritic sst2A labeling were found by immunogold cytochemistry to display low proportions of membrane-associated, as compared with intracellular, receptors. Conversely, in regions displaying diffuse sst2A receptor labeling, receptors were predominantly associated with neuronal plasma membranes, a finding consistent with the high density of sst2 binding sites previously visualized in these areas by autoradiography. Double-labeling studies demonstrated that in the former but not in the latter regions, sst2A-immunoreactive somata and dendrites were heavily contacted by somatostatin axon terminals. Taken together, these results suggest that the low incidence of membrane-associated receptors observed in regions of somatodendritic sst2A labeling may be caused by downregulation of cell surface receptors by endogenous somatostatin, possibly through ligand-induced receptor internalization.
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Perry SF, Reid SG, Wankiewicz E, Iyer V, Gilmour KM. Physiological Responses of Rainbow Trout (Oncorhynchus mykiss) to Prolonged Exposure to Soft Water. ACTA ACUST UNITED AC 1996. [DOI: 10.1086/physzool.69.6.30164267] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Cho K, Yang S, Hu C, Bercu B. Growth Hormone (GH) Response to Growth Hormone-Releasing Hormone (GHRH) Varies with Intrinsic Growth Hormone Secretory Rhythm in Children: Can Somatostatin Pretreatment Reduce This Variability? ACTA ACUST UNITED AC 1992. [DOI: 10.1515/jpem.1992.5.3.155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Robinson IC. The growth hormone secretory pattern: a response to neuroendocrine signals. ACTA PAEDIATRICA SCANDINAVICA. SUPPLEMENT 1991; 372:70-8; discussion 79-80. [PMID: 1681678 DOI: 10.1111/j.1651-2227.1991.tb17975.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- I C Robinson
- Division of Neurophysiology and Neuropharmacology, National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK
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Abstract
With the advent of genetic engineering, the importance of GH in the regulation of growth and metabolism in domestic species has been clearly demonstrated. Ample evidence of an integral role for GH in the processes of growth and lactation exists in dairy cattle (1,2), sheep (3), beef cattle (4) and swine (5). For example, circulating GH levels are high during the period of rapid growth in several species including cattle (6), swine (7) and poultry (8). Endogenous GH secretion is primarily controlled by the central nervous system (CNS) via two specific hypothalamic neurohormones, growth hormone-releasing factor (GRF) and somatostatin (SRIF), an inhibitor of GH release. The secretion of GRF and SRIF is governed by a host of neuropeptides and neurotransmitters which provide a functional link between higher CNS centers and hypophysiotropic neurons. This review will focus on the CNS regulation of GH secretion and circulating factors which feedback to either stimulate or inhibit its release.
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Affiliation(s)
- F C Buonomo
- Animal Sciences Division Monsanto Company, St. Louis, Missouri 63198
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Hormonal Regulation of Male-specific Rat Hepatic Cytochrome P-450g (P-450IIC13) by Androgens and the Pituitary. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)47251-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Reichlin S. Prolactin and growth hormone secretion in stress. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1988; 245:353-76. [PMID: 3067562 DOI: 10.1007/978-1-4899-2064-5_28] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- S Reichlin
- Tufts University School of Medicine, Boston, MA
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Nagasawa H, Nakayama J, Namiki H. Inhibition by SMS 201-995 of normal mammary gland growth in mice. EXPERIENTIA 1987; 43:417-9. [PMID: 2883024 DOI: 10.1007/bf01940434] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Twice daily s.c. injection of 5 ng or 50 ng of SMS 201-995 between 25 and 55 days of age induced a significant retardation of normal mammary gland growth in C3H/He virgin mice, associated with the reduced plasma GH level. Meanwhile, plasma prolactin level and the pattern of estrous cycle were affected little by SMS treatments. The results indicate an involvement of GH in normal mammary gland growth in mice.
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