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Morphological and Functional Changes of Pituitary GH and PRL Cells Following Prolonged Exposure of Female Rats to Constant Light. SERBIAN JOURNAL OF EXPERIMENTAL AND CLINICAL RESEARCH 2021. [DOI: 10.2478/sjecr-2019-0063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Light regulates numerous physiological functions including secretion of different hormones. Our aim was to determine morphological and functional changes of the pituitary growth hormone (GH) and prolactin (PRL) producing cells in female rats exposed to constant light regime from the peripubertal to adult period of life. Starting from the thirtieth postnatal day, female Wistar rats were exposed to constant light (600 lx) for the following 95 days. Controls were maintained under the regular laboratory lighting conditions. The GH and PRL cells were immunohistochemically visualized. Changes in cell volumes and volume densities were evaluated by stereology. Concentrations of PRL and GH in circulation were also determined. We detected significant decrease of the GH cell volume and volume density, followed by reduced the GH blood concentration in comparison to the controls. In contrast, PRL cells were larger in size and their volume density was significantly increased when compared to the controls. Accordingly, PRL concentration was elevated. It can be concluded that exposure of female rats to constant light regime, from peripubertal to adult period of life, causes inhibition of the pituitary GH and stimulation of PRL cells.
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Ciani E, Haug TM, Maugars G, Weltzien FA, Falcón J, Fontaine R. Effects of Melatonin on Anterior Pituitary Plasticity: A Comparison Between Mammals and Teleosts. Front Endocrinol (Lausanne) 2020; 11:605111. [PMID: 33505357 PMCID: PMC7831660 DOI: 10.3389/fendo.2020.605111] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 11/12/2020] [Indexed: 01/01/2023] Open
Abstract
Melatonin is a key hormone involved in the photoperiodic signaling pathway. In both teleosts and mammals, melatonin produced in the pineal gland at night is released into the blood and cerebrospinal fluid, providing rhythmic information to the whole organism. Melatonin acts via specific receptors, allowing the synchronization of daily and annual physiological rhythms to environmental conditions. The pituitary gland, which produces several hormones involved in a variety of physiological processes such as growth, metabolism, stress and reproduction, is an important target of melatonin. Melatonin modulates pituitary cellular activities, adjusting the synthesis and release of the different pituitary hormones to the functional demands, which changes during the day, seasons and life stages. It is, however, not always clear whether melatonin acts directly or indirectly on the pituitary. Indeed, melatonin also acts both upstream, on brain centers that control the pituitary hormone production and release, as well as downstream, on the tissues targeted by the pituitary hormones, which provide positive and negative feedback to the pituitary gland. In this review, we describe the known pathways through which melatonin modulates anterior pituitary hormonal production, distinguishing indirect effects mediated by brain centers from direct effects on the anterior pituitary. We also highlight similarities and differences between teleosts and mammals, drawing attention to knowledge gaps, and suggesting aims for future research.
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Affiliation(s)
- Elia Ciani
- Department of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
| | - Trude M. Haug
- Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway
| | - Gersende Maugars
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway
| | - Finn-Arne Weltzien
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway
| | - Jack Falcón
- Laboratoire Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), MNHN, CNRS FRE 2030, SU, IRD 207, UCN, UA, Paris, France
| | - Romain Fontaine
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway
- *Correspondence: Romain Fontaine,
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Fideleff HL, Fideleff G, Boquete HR, Suárez M, Azaretzky M, Brunetto O. Decreased 6-Sulfatoxymelatonin Excretion in Male GH-Deficient Children and Adolescents. Horm Res Paediatr 2016; 84:88-93. [PMID: 26044919 DOI: 10.1159/000430093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 04/10/2015] [Indexed: 11/19/2022] Open
Abstract
AIM To evaluate melatonin secretion in a group of untreated and treated male growth hormone (GH)-deficient children and adolescents. METHODS We studied 44 male subjects: 8 untreated GH-deficient patients (GHDnt), 16 treated GH-deficient patients (GHDt) and 20 healthy children and adolescents as control group (CG). We measured urinary 6-sulfatoxymelatonin (6-SM) in total (24-hour samples), nocturnal (18.00-8.00 h) and diurnal samples (8.00-18.00 h). Levels of 6-SM were expressed as micrograms excreted per time interval and x0394; values (difference between nighttime and daytime values). RESULTS Significant differences were observed among the 3 groups of pediatric subjects studied for total 6-SM (p < 0.0001), nocturnal 6-SM (p < 0.0001) and x0394; values (p < 0.0001). Subsequent analysis showed significantly higher levels for total 6-SM, nocturnal 6-SM and nighttime-daytime x0394; in the CG versus the GHDnt (p < 0.01) and in the CG versus the GHDt group (p < 0.01). No significant correlations were found between 6-SM excretion and insulin-like growth factor-1 values in the children and adolescents studied. CONCLUSIONS GH-deficient patients showed lower levels of 6-SM. Our findings provide a different insight to a further understanding of some chronobiological disorders involved in GH deficiency in children.
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Affiliation(s)
- Hugo L Fideleff
- Endocrinology Unit, Department of Medicine, Hospital T. Alvarez, Buenos Aires, Argentina
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Mei Y, Duan C, Li X, Zhao Y, Cao F, Shang S, Ding S, Yue X, Gao G, Yang H, Shen L, Feng X, Jia J, Tong Z, Yang X. Reduction of Endogenous Melatonin Accelerates Cognitive Decline in Mice in a Simulated Occupational Formaldehyde Exposure Environment. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2016; 13:ijerph13030258. [PMID: 26938543 PMCID: PMC4808921 DOI: 10.3390/ijerph13030258] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 01/20/2016] [Accepted: 01/27/2016] [Indexed: 01/10/2023]
Abstract
Individuals afflicted with occupational formaldehyde (FA) exposure often suffer from abnormal behaviors such as aggression, depression, anxiety, sleep disorders, and in particular, cognitive impairments. Coincidentally, clinical patients with melatonin (MT) deficiency also complain of cognitive problems associated with the above mental disorders. Whether and how FA affects endogenous MT metabolism and induces cognitive decline need to be elucidated. To mimic occupational FA exposure environment, 16 healthy adult male mice were exposed to gaseous FA (3 mg/m3) for 7 consecutive days. Results showed that FA exposure impaired spatial memory associated with hippocampal neuronal death. Biochemical analysis revealed that FA exposure elicited an intensive oxidative stress by reducing systemic glutathione levels, in particular, decreasing brain MT concentrations. Inversely, intraperitoneal injection of MT markedly attenuated FA-induced hippocampal neuronal death, restored brain MT levels, and reversed memory decline. At tissue levels, injection of FA into the hippocampus distinctly reduced brain MT concentrations. Furthermore, at cellular and molecular levels, we found that FA directly inactivated MT in vitro and in vivo. These findings suggest that MT supplementation contributes to the rescue of cognitive decline, and may alleviate mental disorders in the occupational FA-exposed human populations.
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Affiliation(s)
- Yufei Mei
- Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
- Alzheimer's Disease Center, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
| | - Chunli Duan
- Department of Neuobiology, Capital Medical University, Beijing 100069, China.
| | - Xiaoxiao Li
- Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
| | - Yun Zhao
- Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
| | - Fenghua Cao
- Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
| | - Shuai Shang
- Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
| | - Shumao Ding
- Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
| | - Xiangpei Yue
- Alzheimer's Disease Center, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
| | - Ge Gao
- Department of Neuobiology, Capital Medical University, Beijing 100069, China.
| | - Hui Yang
- Department of Neuobiology, Capital Medical University, Beijing 100069, China.
| | - Luxi Shen
- Alzheimer's Disease Center, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
| | - Xueyan Feng
- Alzheimer's Disease Center, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
| | - Jianping Jia
- Alzheimer's Disease Center, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
| | - Zhiqian Tong
- Alzheimer's Disease Center, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
| | - Xu Yang
- Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
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Fideleff HL, Fideleff G, Boquete HR, Suárez M, Azaretzky M. Male-female differences in 6-sulfatoxymelatonin excretion in hypopituitary patients. ARCHIVES OF ENDOCRINOLOGY AND METABOLISM 2016; 60:223-30. [PMID: 26886086 PMCID: PMC10522305 DOI: 10.1590/2359-3997000000153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 12/16/2015] [Indexed: 06/05/2023]
Abstract
OBJECTIVE To evaluate melatonin secretion in adult hypopituitary patients with Growth Hormone deficiency (AGHD) on and off replacement therapy. SUBJECTS AND METHODS We studied 48 subjects: 12 (6 males) untreated AGHD (AGHDnt), 20 (10 males) treated AGHD (AGHDt) and 16 healthy subjects (8 males) as control group (CG). We measured urinary 6-sulfatoxymelatonin (6-SM) in total (24 h samples), nocturnal (6-SMn): 1800-0800 and diurnal samples (6-SMd): 0800-1800. RESULTS Significant differences were observed among the 3 groups of male subjects, in total 6-SM (p < 0.05), nocturnal 6-SM (p < 0.02) and nighttime-daytime delta values (p < 0.003). CG had significantly higher values than the AGHDnt in total 6-SM (p < 0.01), nocturnal 6-SM (p < 0.05) and nighttime-daytime delta values (p < 0.01). AGHDt patients showed significantly higher levels in nighttime-daytime delta values than AGHDnt patients (p < 0.05). In females, no significant differences were found among the 3 groups studied in total, nocturnal, diurnal or nighttime-daytime delta values. In males, significant correlations were found among total 6-SM (r = 0.58; p = 0.029), nocturnal 6-SM (r = 0.70; p = 0.006) and nighttime-daytime delta values (r = 0.71; p = 0.004) vs. serum IGF-1 levels in subjects evaluated. In females, significant correlations were found among total 6-SM (r = 0.57; p = 0.02) vs. serum IGF-1 levels in subjects evaluated. A tendency towards a significant correlation was found in diurnal 6-SM (r = 0.48; p = 0.07). CONCLUSIONS Our findings show a sexual dimorphism in 6-SM excretion in AGHD patients and provide an interesting approach to a further understanding of some chronobiological disorders involved in GH deficiency.
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Affiliation(s)
- Hugo L. Fideleff
- Unidad de EndocrinologíaDepartamento de MedicinaHospital T. AlvarezBuenos AiresArgentinaUnidad de Endocrinología, Departamento de Medicina, Hospital T. Alvarez, Buenos Aires, Argentina
| | - Gabriel Fideleff
- Unidad de EndocrinologíaDepartamento de MedicinaHospital T. AlvarezBuenos AiresArgentinaUnidad de Endocrinología, Departamento de Medicina, Hospital T. Alvarez, Buenos Aires, Argentina
| | - Hugo R. Boquete
- Unidad de EndocrinologíaDepartamento de MedicinaHospital T. AlvarezBuenos AiresArgentinaUnidad de Endocrinología, Departamento de Medicina, Hospital T. Alvarez, Buenos Aires, Argentina
| | - Martha Suárez
- Unidad de EndocrinologíaDepartamento de MedicinaHospital T. AlvarezBuenos AiresArgentinaUnidad de Endocrinología, Departamento de Medicina, Hospital T. Alvarez, Buenos Aires, Argentina
| | - Miriam Azaretzky
- Unidad de EndocrinologíaDepartamento de MedicinaHospital T. AlvarezBuenos AiresArgentinaUnidad de Endocrinología, Departamento de Medicina, Hospital T. Alvarez, Buenos Aires, Argentina
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Filippa V, Mohamed F. Morphological and Morphometric Changes of Pituitary Lactotrophs of Viscacha (Lagostomus maximus maximus) in Relation to Reproductive Cycle, Age, and Sex. Anat Rec (Hoboken) 2009; 293:150-61. [DOI: 10.1002/ar.21013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Chowdhury VS, Yamamoto K, Saeki I, Hasunuma I, Shimura T, Tsutsui K. Melatonin stimulates the release of growth hormone and prolactin by a possible induction of the expression of frog growth hormone-releasing peptide and its related peptide-2 in the amphibian hypothalamus. Endocrinology 2008; 149:962-70. [PMID: 18063680 DOI: 10.1210/en.2007-1427] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We recently identified a novel hypothalamic neuropeptide stimulating GH release in bullfrogs and termed it frog GH-releasing peptide (fGRP). The fGRP precursor encodes fGRP and its related peptides (fGRP-RP-1, -RP-2, and -RP-3), and fGRP-RP-2 also stimulates GH and prolactin (PRL) release. Cell bodies and terminals containing these neuropeptides are localized in the suprachiasmatic nucleus (SCN) and median eminence, respectively. To understand the physiological role of fGRP and fGRP-RP-2, we investigated the mechanisms that regulate the expression of these neuropeptides. This study shows that melatonin induces the expression of fGRP and fGRP-RPs in bullfrogs. Orbital enucleation combined with pinealectomy (Ex plus Px) decreased the expression of fGRP precursor mRNA and content of mature fGRP and fGRP-RPs in the diencephalon including the SCN and median eminence. Conversely, melatonin administration to Ex plus Px bullfrogs increased dose-dependently their expressions. The expression of fGRP precursor mRNA was photoperiodically controlled and increased under short-day photoperiods, when the nocturnal duration of melatonin secretion increases. To clarify the mode of melatonin action on the induction of fGRP and fGRP-RPs, we further demonstrated the expression of Mel(1b), a melatonin receptor subtype, in SCN neurons expressing fGRP precursor mRNA. Finally, we investigated circulating GH and PRL levels after melatonin manipulation because fGRP and fGRP-RP-2 stimulate the release of GH and GH/PRL, respectively. Ex plus Px decreased plasma GH and PRL concentrations, whereas melatonin administration increased these hormone levels. These results suggest that melatonin induces the expression of fGRP and fGRP-RP-2, thus stimulating the release of GH and PRL in bullfrogs.
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Affiliation(s)
- Vishwajit S Chowdhury
- Laboratory of Integrative Brain Sciences, Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 1-6-1 Nishi-Waseda, Shinjuku-ku, Tokyo 169-8050, Japan.
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Chodick G, Shalev V, Goren I, Inskip PD. Seasonality in Birth Weight in Israel: New Evidence Suggests Several Global Patterns and Different Etiologies. Ann Epidemiol 2007; 17:440-6. [PMID: 17300954 DOI: 10.1016/j.annepidem.2006.10.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 10/12/2006] [Indexed: 10/23/2022]
Abstract
PURPOSE To investigate the effect of season on birth weight and whether it is expressed also in fluctuations of proportions of extreme birth weights. METHODS Information about 225,545 singletons born during 1998 to 2004 was obtained from a large health maintenance organization in Israel. We conducted a linear regression analysis of the weight with month and year of birth, sex, maternal age, diabetes, and several meteorological factors as independent variables, which were also incorporated into multivariate logistic regression models to examine the effect of season of birth on the frequency of low birth weight (LBW, <2500 g) or macrosomia (>4000 g). RESULTS A significant (P < .001) seasonal pattern in birth weights was observed, with a peak in July and a trough in January. Babies born in summer had an OR of 1.12 (95% CI; 1.07 to 1.18) for macrosomia compared with those born in the winter. No such pattern was found for LBW. CONCLUSIONS While in regions of mid-latitude, summer is associated with relatively lower birth weight, possibly because of exposure to cold temperature during early or mid-pregnancy, our data suggest that in Israel, the peak birth weight is in summer, possibly because of increased exposure to sunlight in the last weeks of the pregnancy.
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Affiliation(s)
- Gabriel Chodick
- Medical Informatics Department, Maccabi Healthcare Services , Tel-Aviv, Israel.
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Filippa V, Mohamed F. Immunohistochemical study of somatotrophs in pituitary pars distalis of male viscacha (Lagostomus maximus maximus) in relation to the gonadal activity. Cells Tissues Organs 2007; 184:188-97. [PMID: 17409745 DOI: 10.1159/000099626] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2006] [Indexed: 11/19/2022] Open
Abstract
Somatotrophs were identified and quantified in pituitary pars distalis of male viscachas (Lagostomus maximus maximus) during the annual reproductive cycle, after the administration of melatonin, after castration and in different growth stages by immunohistochemistry and morphometric analysis. In adult male viscachas, the somatotrophs were distributed throughout the pars distalis during the reproductive cycle. They were oval, pyramidal or round in shape with a large round nucleus. The percentage immunopositive area, the major cellular diameter and the number of cells decreased during the gonadal regression period in relation to the values found in the reproductive period. The administration of melatonin did not provoke any variations of the morphometric parameters studied. On the contrary, a significant decrease in the percentage immunopositive area, in the major cellular diameter and in the number of somatotrophs in castrated viscachas was observed. The study of different growth stages showed that these morphometric parameters increased from immature to adult animals in the reproductive period. The results obtained suggested that the variations of the morphometric parameters of somatotrophs are more related to the gonadal development and activity than to a direct effect of melatonin.
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Affiliation(s)
- V Filippa
- Cátedra de Histología y Embriología, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, San Luis, Argentina.
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Kasuya E, Kushibiki S, Sutoh M, Saito T, Ito S, Yayou KI, Sakumoto R, Hodate K. Effect of melatonin injected into the third ventricle on growth hormone secretion in Holstein steers. J Vet Med Sci 2006; 68:1075-80. [PMID: 17085886 DOI: 10.1292/jvms.68.1075] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of melatonin (MEL) injection into the third ventricle (3V) on growth hormone (GH) secretion were investigated in conscious Holstein steers. A stainless steel cannula was stereotaxically implanted in the 3V based on the ventriculogram. In Exp. 1, three doses of MEL (100, 300 or 600 microg) were injected into the 3V through the cannula and the GH concentration after the injection was determined. In Exp. 2, intracerebroventricular (icv) and intravenous (iv) injections of MEL (100 microg) and GH-releasing hormone (GHRH; 0.25 microg/kg body weight), respectively, were performed simultaneously to examine the effect of MEL on GHRH-induced GH release. The icv injection of MEL significantly stimulated GH release at 100 microg. The increase in GH concentrations by 100 microg of MEL was persistent. Intravenous injection of GHRH dramatically increased GH release. The injection of MEL did not alter GHRH-induced GH release. These results suggest that MEL stimulates GH secretion possibly through the hypothalamus in cattle.
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Affiliation(s)
- Etsuko Kasuya
- Department of Physiology and Genetic Regulation, National Institute of Agrobiological Sciences, Ibaraki, Japan
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Forbes D, Jansen SL, Duncan V, Morgan DG. Melatonin for cognitive impairment. THE COCHRANE DATABASE OF SYSTEMATIC REVIEWS 2005. [DOI: 10.1002/14651858.cd003802.pub2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Mustonen AM, Nieminen P, Asikainen J, Saarela S, Kukkonen JVK, Hyvärinen H. Continuous Melatonin Treatment and Fasting in the Raccoon Dog (Nyctereutes procyonoides) – Vernal Body Weight Regulation and Reproduction. Zoolog Sci 2004; 21:163-72. [PMID: 14993828 DOI: 10.2108/zsj.21.163] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The raccoon dog (Nyctereutes procyonoides) is a canid omnivore with marked seasonal changes in its body adiposity. The aim of this study was to investigate the roles of melatonin, leptin, ghrelin and growth hormone (GH) in weight regulation and reproduction of the species. Sixteen raccoon dogs were treated with continuous-release melatonin implants in Aug 2000 and in Feb 2001 (the MEL group) and 16 animals were sham-operated (the SHAM group). Half of the raccoon dogs were fasted between Nov 27(th) 2000 and Jan 25(th) 2001. The autumnal results have been previously published and this paper reports the vernal data. The leptin concentrations of the SHAM females were high before the mating season, decreased before estrus, increased during gestation and reduced after parturition. The MEL females had higher leptin concentrations than the SHAM females in early March, whereas the MEL males had lower leptin concentrations than the SHAM males in late March. Also the ghrelin and GH concentrations of the SHAM females decreased before estrus. Continuous melatonin treatment advanced the vernal rise in the ghrelin concentrations and the vernal drop and the subsequent rise in the GH concentrations of the females. Melatonin also increased their body mass indices from July to Aug 2001, indicating that it triggers the autumnal accumulation of fat in the species.
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Juszczak M, Stempniak B. The effect of melatonin on suckling-induced oxytocin and prolactin release in the rat. Brain Res Bull 1997; 44:253-8. [PMID: 9323439 DOI: 10.1016/s0361-9230(97)00117-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
There is growing evidence that melatonin (MEL) inhibits oxytocin (OT) release when used in a low dose, while higher doses stimulate the release of the hormone in the rat. In the present study we investigated the effect of exogenous MEL, administered intracerebroventricularly (ICV), on suckling-induced OT and prolactin (PRL) release in the urethane-anesthetized rat. Lactating rats suckled by 8-12 pups were studied on days 8-12 of postpartum, and lactating pups-deprived rats on the same days of postpartum served as a control. Plasma OT and PRL levels as well as hypothalamic and neurohypophyseal OT contents were measured by RIA. Suckling stimulated the secretion of both OT and PRL. The ICV injection of 1 ng/ml MEL produced a significant inhibition of suckling-induced OT as well as PRL secretion. Melatonin in doses of 100 ng/ml or 10 micrograms/ml did not modify the OT release but significantly inhibited PRL release brought about by suckling; 10 pg/ml of MEL was not effective in this regard. Thus, exogenous MEL seems to inhibit suckling-induced OT as well as PRL secretion when applied at doses regarded to be in the range of the physiological level; when applied in higher doses, it was shown not to influence the release of OT following physiological stimulation such as suckling.
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Affiliation(s)
- M Juszczak
- Department of Pathophysiology, Medical University of Lodz, Poland
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Rozell MD, Mead RA. Effect of melatonin on pituitary secretion of prolactin in vitro during delayed implantation and the periimplantation period in the spotted skunk. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1993; 267:524-32. [PMID: 8263466 DOI: 10.1002/jez.1402670507] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The pars tuberalis of the western spotted skunk is the only region of the brain known to bind 2-[125I]iodomelatonin, thus suggesting that this region of the pituitary might be essential in mediating the effects of melatonin in this species. Female skunks were killed during short- and long-day photoperiods. Hemisections of the adenohypophysis, with and without the pars tuberalis were cultured in the presence and absence of 10 nM melatonin to determine whether the pars tuberalis mediates the previously observed suppressive effects of melatonin on the seasonal increase in plasma prolactin levels in this species. Pituitaries obtained during long-day photoperiods secreted significantly more prolactin than those obtained during the short-day photoperiod. Melatonin had no effect on pituitary response to gonadotropin releasing hormone and failed to inhibit prolactin secretion during the 48 h culture period. However, melatonin significantly reduced the inhibitory effects of dopamine on prolactin secretion. The latter response was observed in both photoperiods and in the presence and absence of the pars tuberalis. These results suggest that the pars tuberalis does not mediate the inhibitory effect of melatonin on prolactin secretion in the absence of the hypothalamus.
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Affiliation(s)
- M D Rozell
- Department of Biological Sciences, University of Idaho, Moscow 83843
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Valcavi R, Zini M, Maestroni GJ, Conti A, Portioli I. Melatonin stimulates growth hormone secretion through pathways other than the growth hormone-releasing hormone. Clin Endocrinol (Oxf) 1993; 39:193-9. [PMID: 8370132 DOI: 10.1111/j.1365-2265.1993.tb01773.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
OBJECTIVE There is evidence that melatonin plays a role in the regulation of GH secretion. The aim of this study was to investigate the neuroendocrine mechanisms by which melatonin modulates GH secretion. Thus we assessed the effect of oral melatonin on the GH responses to GHRH administration and compared the effects of melatonin with those of pyridostigmine, a cholinergic agonist drug which is likely to suppress hypothalamic somatostatin release. DESIGN The study consisted of four protocols carried out during the afternoon hours. Study 1: oral melatonin (10 mg) or placebo were administered 60 minutes prior to GHRH (100 micrograms i.v. bolus). Study 2: GHRH (100 micrograms i.v. bolus) or placebo were administered at 0 minutes; oral melatonin or placebo were given at 60 minutes and were followed by a second GHRH stimulus (100 micrograms i.v. bolus) at 120 minutes. Study 3: placebo; oral melatonin (10 mg); oral pyridostigmine (120 mg); melatonin (10 mg) plus pyridostigmine (120 mg) were administered on separate occasions. Study 4: placebo; oral melatonin (10 mg); oral pyridostigmine (120 mg); melatonin (10 mg) plus pyridostigmine (120 mg) were administered on separate occasions 60 minutes prior to a submaximal dose (3 micrograms i.v. bolus) of GHRH. SUBJECTS Four groups of eight normal male subjects, ages 22-35 years, were randomly assigned to each protocol. MEASUREMENTS Growth hormone was measured by RIA at 15-minute intervals. RESULTS Oral melatonin administration had a weak stimulatory effect on GH basal levels. Prior melatonin administration approximately doubled the GH release induced by supramaximal (100 micrograms) or submaximal (3 micrograms) doses of GHRH. Melatonin administration restored the GH response to a second GHRH challenge, given 120 minutes after a first GHRH i.v. bolus. The GH releasing effects of pyridostigmine, either alone or followed by GHRH, were greater than those of melatonin. However, the simultaneous administration of melatonin and pyridostigmine was not followed by any further enhancement of GH release, either in the absence or in the presence of exogenous GHRH. CONCLUSIONS Our data indicate that oral administration of melatonin to normal human males increases basal GH release and GH responsiveness to GHRH through the same pathways as pyridostigmine. Therefore it is likely that melatonin plays this facilitatory role at the hypothalamic level by inhibiting endogenous somatostatin release, although with a lower potency than pyridostigmine. The physiological role of melatonin in GH neuroregulation remains to be established.
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Affiliation(s)
- R Valcavi
- 2a Divisione di Medicina Interna, Arcispedale S. Maria Nuova, Reggio Emilia, Italy
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16
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Abstract
The effect of melatonin as well as pinealectomy on the basal and K(+)-evoked release of vasopressin and oxytocin from the neurointermediate lobes in vitro was determined. Pineal removal resulted in a diminution of vasopressin and oxytocin release from the neurointermediate lobes in vitro. Melatonin (10(-3) or 10(-6) M/l) increased vasopressin and oxytocin release from neurointermediate lobes of sham-operated rats. Nevertheless, when pinealectomized rats served as donors of the neurointermediate lobes, melatonin (10(-3) or 10(-6) M/l) increased vasopressin release under basal conditions. For the same tissue, melatonin did not affect the oxytocin release either under basal conditions or during depolarization due to excess potassium. When 10(-7) M/l melatonin was used, no changes in either vasopressin or oxytocin release were observed in vitro.
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Affiliation(s)
- M Juszczak
- Department of Pathophysiology, School of Medicine, Lodz, Poland
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17
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Abstract
Two experiments were designed to determine which tissues accumulate [3H]-melatonin and the metabolic fate of this hormone in the spotted skunk. Tritiated melatonin was injected into the jugular vein of 10 anesthetized skunks 1-3 h before the onset of darkness and allowed to circulate for 22 min before the vasculature was flushed with saline to clear radioactivity from the blood. Selected tissues were removed from five skunks and oxidized in a Packard Biological Oxidizer which yielded 95 +/- 5% recovery of radioactivity. Relatively high amounts of radioactivity were found in the pineal (367 +/- 304 dpm/mg tissue), ovary (69 +/- 38 dpm/mg), pituitary (89 +/- 56 dpm/mg), liver (107 +/- 29 dpm/mg), and kidney (63 +/- 15 dpm/mg). Relatively small amounts of [3H] were found in different brain regions (approximately 6-7 dpm/mg). The uterus, pancreas, and temporalis muscle also accumulated radioactivity (approximately 13 dpm/mg). The lung retained the least amount of radioactivity (4 +/- 1.3 dpm/mg). In the second experiment, hypothalami, pituitaries, and ovaries were removed from the remaining five females. Radioactivity from these tissues was extracted and subjected to thin-layer chromatography. Melatonin accounted for approximately 70% of the radioactivity recovered while 6-hydroxymelatonin and unidentified more polar compounds made up the majority of the melatonin metabolites. These data indicate that tissues other than the hypothalamus are able to accumulate [3H]-melatonin.
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Affiliation(s)
- M Berria
- Department of Biological Sciences, University of Idaho, Moscow 83843
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