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Marshall CJ, Blake A, Stewart C, Liddle TA, Denizli I, Cuthill F, Evans NP, Stevenson TJ. Prolactin Mediates Long-Term, Seasonal Rheostatic Regulation of Body Mass in Female Mammals. Endocrinology 2024; 165:bqae020. [PMID: 38417844 PMCID: PMC10904104 DOI: 10.1210/endocr/bqae020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 01/31/2024] [Accepted: 02/27/2024] [Indexed: 03/01/2024]
Abstract
A series of well-described anabolic and catabolic neuropeptides are known to provide short-term, homeostatic control of energy balance. The mechanisms that govern long-term, rheostatic control of regulated changes in energy balance are less well characterized. Using the robust and repeatable seasonal changes in body mass observed in Siberian hamsters, this report examined the role of prolactin in providing long-term rheostatic control of body mass and photoinduced changes in organ mass (ie, kidney, brown adipose tissue, uterine, and spleen). Endogenous circannual interval timing was observed after 4 months in a short photoperiod, indicated by a significant increase in body mass and prolactin mRNA expression in the pituitary gland. There was an inverse relationship between body mass and the expression of somatostatin (Sst) and cocaine- and amphetamine-regulated transcript (Cart). Pharmacological inhibition of prolactin release (via bromocriptine injection), reduced body mass of animals maintained in long photoperiods to winter-short photoperiod levels and was associated with a significant increase in hypothalamic Cart expression. Administration of ovine prolactin significantly increased body mass 24 hours after a single injection and the effect persisted after 3 consecutive daily injections. The data indicate that prolactin has pleiotropic effects on homeostatic sensors of energy balance (ie, Cart) and physiological effectors (ie, kidney, BAT). We propose that prolactin release from the pituitary gland acts as an output signal of the hypothalamic rheostat controller to regulate adaptive changes in body mass.
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Affiliation(s)
- Christopher J Marshall
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - Alexandra Blake
- Institute of Molecular Biology, University of Mainz, Mainz 55122, Germany
| | - Calum Stewart
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - T Adam Liddle
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Irem Denizli
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Fallon Cuthill
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Neil P Evans
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Tyler J Stevenson
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
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Stewart C, Marshall CJ. Seasonality of prolactin in birds and mammals. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2022; 337:919-938. [PMID: 35686456 PMCID: PMC9796654 DOI: 10.1002/jez.2634] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 04/21/2022] [Accepted: 05/23/2022] [Indexed: 01/07/2023]
Abstract
In most animals, annual rhythms in environmental cues and internal programs regulate seasonal physiology and behavior. Prolactin, an evolutionarily ancient hormone, serves as a molecular correlate of seasonal timing in most species. Prolactin is highly pleiotropic with a wide variety of well-documented physiological effects; in a seasonal context prolactin is known to regulate annual changes in pelage and molt. While short-term homeostatic variation of prolactin secretion is under the control of the hypothalamus, long-term seasonal rhythms of prolactin are programmed by endogenous timers that reside in the pituitary gland. The molecular basis of these rhythms is generally understood to be melatonin dependent in mammals. Prolactin rhythmicity persists for several years in many species, in the absence of hypothalamic signaling. Such evidence in mammals has supported the hypothesis that seasonal rhythms in prolactin derive from an endogenous timer within the pituitary gland that is entrained by external photoperiod. In this review, we describe the conserved nature of prolactin signaling in birds and mammals and highlight its role in regulating multiple diverse physiological systems. The review will cover the current understanding of the molecular control of prolactin seasonality and propose a mechanism by which long-term rhythms may be generated in amniotes.
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Affiliation(s)
- Calum Stewart
- Institute of Biodiversity, Animal Health & Comparative MedicineUniversity of GlasgowGlasgowUK
| | - Christopher J. Marshall
- Institute of Biodiversity, Animal Health & Comparative MedicineUniversity of GlasgowGlasgowUK
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Ni Y, Chen Q, Cai J, Xiao L, Zhang J. Three lactation-related hormones: Regulation of hypothalamus-pituitary axis and function on lactation. Mol Cell Endocrinol 2021; 520:111084. [PMID: 33232781 DOI: 10.1016/j.mce.2020.111084] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 10/08/2020] [Accepted: 11/11/2020] [Indexed: 01/10/2023]
Abstract
The endocrine system plays a central role in many aspects of lactation, including mammogenesis (mammary gland development), lactogenesis (onset of lactation), and galactopoiesis (maintenance of milk secretion). Many hormones of the endocrine system directly or indirectly regulate lactation process. The secretion of prolactin (PRL), one of the most important lactation-related hormones, is inhibited by hypothalamus-pituitary dopaminergic system and stimulated by hypothalamus-pituitary oxytocinergic system. This hormone is essential in all stages of lactation. The growth hormone (GH) regulates metabolism and the distribution of nutrients between tissues mammary glands, and stimulates the production of IGF-I from the liver which binds to IGF-IR of mammary epithelial cells (MECs) to indirectly promote lactation. The synthesis and secretion of estrogen (E) are affected by the hypothalamus-pituitary axis. The hormone regulates duct morphogenesis and MECs proliferation. It also modulates the synthesis and secretion of PRL and GH, which together regulate the lactation in female animals. In this article, we reviewed the three main lactation-related hormones (PRL, GH, and E), summarize their regulation by the hypothalamus-pituitary axis and how they influence lactation.
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Affiliation(s)
- Yifan Ni
- College of Animal Science, Zhejiang University, Hangzhou, 310058, China
| | - Qiangqiang Chen
- College of Animal Science, Zhejiang University, Hangzhou, 310058, China
| | - Jianfeng Cai
- College of Animal Science, Zhejiang University, Hangzhou, 310058, China
| | - Lixia Xiao
- College of Animal Science, Zhejiang University, Hangzhou, 310058, China
| | - Jinzhi Zhang
- College of Animal Science, Zhejiang University, Hangzhou, 310058, China.
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Abstract
The hypothalamic control of prolactin secretion is different from other anterior pituitary hormones, in that it is predominantly inhibitory, by means of dopamine from the tuberoinfundibular dopamine neurons. In addition, prolactin does not have an endocrine target tissue, and therefore lacks the classical feedback pathway to regulate its secretion. Instead, it is regulated by short loop feedback, whereby prolactin itself acts in the brain to stimulate production of dopamine and thereby inhibit its own secretion. Finally, despite its relatively simple name, prolactin has a broad range of functions in the body, in addition to its defining role in promoting lactation. As such, the hypothalamo-prolactin axis has many characteristics that are quite distinct from other hypothalamo-pituitary systems. This review will provide a brief overview of our current understanding of the neuroendocrine control of prolactin secretion, in particular focusing on the plasticity evident in this system, which keeps prolactin secretion at low levels most of the time, but enables extended periods of hyperprolactinemia when necessary for lactation. Key prolactin functions beyond milk production will be discussed, particularly focusing on the role of prolactin in inducing adaptive responses in multiple different systems to facilitate lactation, and the consequences if prolactin action is impaired. A feature of this pleiotropic activity is that functions that may be adaptive in the lactating state might be maladaptive if prolactin levels are elevated inappropriately. Overall, my goal is to give a flavour of both the history and current state of the field of prolactin neuroendocrinology, and identify some exciting new areas of research development.
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Affiliation(s)
- David R Grattan
- Centre for Neuroendocrinology and Department of AnatomyUniversity of Otago, PO Box 913, Dunedin 9054, New ZealandMaurice Wilkins Centre for Molecular BiodiscoveryAuckland, New Zealand Centre for Neuroendocrinology and Department of AnatomyUniversity of Otago, PO Box 913, Dunedin 9054, New ZealandMaurice Wilkins Centre for Molecular BiodiscoveryAuckland, New Zealand
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Christensen HR, Zeng Q, Murawsky MK, Gregerson KA. Estrogen regulation of the dopamine-activated GIRK channel in pituitary lactotrophs: implications for regulation of prolactin release during the estrous cycle. Am J Physiol Regul Integr Comp Physiol 2011; 301:R746-56. [PMID: 21653876 DOI: 10.1152/ajpregu.00138.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prolactin (PRL), synthesized and secreted from lactotrophs of the anterior pituitary gland, is tonically inhibited by hypothalamic dopamine (DA) throughout the female reproductive (estrous) cycle. Our laboratory has shown that DA hyperpolarizes these cells by activating G protein-coupled inwardly rectifying K(+) (GIRK) channels; however, this response is only observed on proestrus. While the cellular mechanisms that allow for functional expression of this unique DA-signaling pathway are unclear, we hypothesized that activation of the DA-GIRK effector pathway is due to the rise in circulating estrogen (E₂) during the preceding day of diestrus. Thus, we examined the effects of E₂ on primary lactotrophs isolated from female rats. Treatment with a physiological concentration of E₂ (40-80 pg/ml, in vivo or in vitro) induced a proestrous phenotype in diestrous lactotrophs. These cells exhibited a DA-induced membrane hyperpolarization, as well as a secretory rebound of PRL following DA withdrawal (characteristic of proestrous cells). Internal dialysis of GTPγS demonstrated that E₂ exposure enabled functional expression of GIRK channels, and this regulation by E₂ did not involve the D₂R. The effect of E₂ was blocked by the receptor antagonist, ICI 182,780, and by the protein synthesis inhibitor, cycloheximide. Single-cell analysis revealed increased mRNA expression of GIRK channel subunits in E₂-treated lactotrophs. While E₂ is known to have multiple actions on the lactotroph, the present findings illuminate a novel action of E₂ in lactotrophs-regulation of the expression of a DA effector, the GIRK channel.
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Affiliation(s)
- Heather R Christensen
- James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, Ohio, USA.
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Abstract
Endocrine pituitary cells are neuronlike; they express numerous voltage-gated sodium, calcium, potassium, and chloride channels and fire action potentials spontaneously, accompanied by a rise in intracellular calcium. In some cells, spontaneous electrical activity is sufficient to drive the intracellular calcium concentration above the threshold for stimulus-secretion and stimulus-transcription coupling. In others, the function of these action potentials is to maintain the cells in a responsive state with cytosolic calcium near, but below, the threshold level. Some pituitary cells also express gap junction channels, which could be used for intercellular Ca(2+) signaling in these cells. Endocrine cells also express extracellular ligand-gated ion channels, and their activation by hypothalamic and intrapituitary hormones leads to amplification of the pacemaking activity and facilitation of calcium influx and hormone release. These cells also express numerous G protein-coupled receptors, which can stimulate or silence electrical activity and action potential-dependent calcium influx and hormone release. Other members of this receptor family can activate calcium channels in the endoplasmic reticulum, leading to a cell type-specific modulation of electrical activity. This review summarizes recent findings in this field and our current understanding of the complex relationship between voltage-gated ion channels, ligand-gated ion channels, gap junction channels, and G protein-coupled receptors in pituitary cells.
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Affiliation(s)
- Stanko S Stojilkovic
- Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Building 49, Room 6A-36, 49 Convent Drive, Bethesda, Maryland 20892-4510, USA.
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Samson WK. Putting the brakes on lactotrope hyperplasia. Trends Endocrinol Metab 2006; 17:2-3. [PMID: 16307891 DOI: 10.1016/j.tem.2005.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Revised: 09/30/2005] [Accepted: 11/10/2005] [Indexed: 11/20/2022]
Abstract
Although much is known about the mechanisms by which dopamine, the major regulator of lactotrope function, controls hormone production and secretion, its growth inhibiting actions have remained less well characterized. Recent research has uncovered an important role for endogenously produced transforming growth factor beta (TGFbeta) and TGFbeta receptors in dopamine's ability to put the brakes on lactotrope proliferation. These novel findings promise increased knowledge of the genesis and potential therapeutic control of human prolactinomas.
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Affiliation(s)
- Willis K Samson
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, 1402 South Grand Boulevard, St. Louis, MO 63131, USA.
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Alvarez Alvarado R, Porras Villalobos MG, Calderón Rosete G, Rodríguez Sosa L, Aréchiga H. Dopaminergic Modulation of Neurosecretory Cells in the Crayfish. Cell Mol Neurobiol 2005; 25:345-70. [PMID: 16047546 DOI: 10.1007/s10571-005-3064-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The main aims of this paper are (a) to locate possible dopaminergic neurons in the eyestalk with anti-tyrosine hydroxylase antibodies, (b) to search for the presence of dopamine (DA) in the nervous structures of the eyestalk, (c) to explore its release, and (d) to test the effect of DA on neurosecretory cells in the eyestalk. Experiments were performed in adult crayfishes Procambarus clarkii, in isolated optic peduncle. Immunocytochemistry was made with the antibody against its precursor synthesizing enzyme tyrosine-hydroxylase. The content and release studies of DA were made using high performance liquid chromatography (HPLC). Extracellular and intracellular recordings were conducted with conventional recording techniques. A large number (approximately 2000) of immunopositive somata of different sizes and shapes were identified in various regions of the eyestalk. The majority of somata are of the smallest size (5-25 microm diameter). DA content in the eyestalk was 5.6 +/- 0.1 pmol per structure; the greatest content is in the MT (over 60%). A basal level release of DA was observed. Incubation of eyestalks in solution containing a high K+ concentration increased the DA release (79%). Two effects of DA on the excitability of X-organ neurons were observed; an excitatory effect on neurons of approximately 25 microm somata diameter and another inhibitory effect in the group of approximately 35-microm somata diameter neurons. The excitation occurs with a depolarization and decrement of membrane conductance in the cell soma while the inhibition occurs with a hyperpolarization and increment of membrane conductance in soma. We concluded the following: (1) Dopamine is present in each optic ganglia of the crayfish eyestalk. (2) There is a basal release of DA from the isolated eyestalk. (3) DA release is enhanced threefold by eyestalk incubation in 40 mM [K+] solution. (4) DA selectively excites a population of neurons with low-speed conduction axons, and small somata in the X-organ-sinus gland system, while inhibiting another population characterized by higher axonal conduction speed and large somata. (5) These observations support a role for DA as a neurotransmitter or neuromodulator in the X-organ neurons of the crayfish eyestalk.
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Affiliation(s)
- Ramón Alvarez Alvarado
- División de Estudios de Posgrado e Investigación, Facultad de Medicina, UNAM. ler. Piso Unidad de Posgrado, Ciudad Universitaria, México
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