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The Biochemical Journal Jul 19761. Newly synthesized prolactin was obtained from cultures of rat pituitary tumour cells (GH4C1 cells) after incubation with [35S]methionine. 2. Radioactive synthesized...
1. Newly synthesized prolactin was obtained from cultures of rat pituitary tumour cells (GH4C1 cells) after incubation with [35S]methionine. 2. Radioactive synthesized and secreted prolactin was quantified by an immunoprecipitation method by using disc-gel electrophoresis of the dissolved immunoprecipitate in the presence of sodium dodecyl sulphate. By using a microanalytical modification, hormone synthesis and secretion could also be studied in single-cell cultures. This technique was combined with a cytoimmunofluorescence method in which rhodamine-conjugated antibodies were used for studying intracellular prolactin. 3. The presence of radioactive synthesized and secreted prolactin was demonstrated in nine out of 13 single-cell cultures. Cell cultures containing 10 cells or more and clonal populations originating from one cell always secreted radioactive prolactin. 4. Thyroliberin treatment (2 muM) for 24h increased the extracellular accumulation of radioactive prolactin in five out of seven single-cell cultures and always in populations of cells. 5. The number of cells showing prolactin specific fluorescence increased from 20 to 50% and the intensity of this fluorescence became greater after thyroliberin treatment. 6. Studies of [35S]prolactin secretion from single cells and immunochemical detection of intracellular prolactin showed that some cells in an unsynchronized population did not secret radioactive prolactin or show prolactin specific fluorescence. 7. The quantitative effect of thyroliberin as studied in single-cell cultures suggested that the main if not the only effect was to increase prolactin synthesis in cells already producing hormone.
Topics: Animals; Antigen-Antibody Reactions; Clone Cells; Pituitary Gland; Pituitary Neoplasms; Prolactin; Rats; Thyrotropin-Releasing Hormone
PubMed: 822844
DOI: 10.1042/bj1580119 -
Journal of Dairy Science Jul 2016Dairy cattle require a dry period between successive lactations to ensure optimal milk production. Because prolactin (PRL) is necessary for the initiation and...
Dairy cattle require a dry period between successive lactations to ensure optimal milk production. Because prolactin (PRL) is necessary for the initiation and maintenance of milk production, strategies that can inhibit PRL secretion might hasten the involution process. The objective of this study was to determine the effect of the PRL release inhibitor cabergoline on markers of mammary gland involution during the early dry period. To assess the effect of cabergoline treatment on mammary gland involution, 14 Holstein dairy cows in late lactation were treated with either a single i.m. administration of 5.6mg of cabergoline (Velactis, Ceva Santé Animale, Libourne, France, n=7) or placebo (n=7) at the time of dry-off. Blood samples and mammary secretion samples were collected 6d before dry-off and again 1, 2, 3, 4, 8, and 14d following the abrupt cessation of lactation. Blood samples were used to determine plasma PRL concentrations. Mammary secretion samples were used to determine somatic cell count, milk fat, lactose, true protein content, and concentrations of α-lactalbumin, lactoferrin, and citrate. Following the cessation of lactation, changes in mammary secretion composition indicated diminished milk synthesis, including reduced concentrations of α-lactalbumin, citrate, and lactose. In contrast, milk somatic cell count, percent total protein, percent fat content, and lactoferrin concentrations significantly increased as involution progressed. Cabergoline treatment decreased the plasma PRL concentrations during the first week of dry-off, compared with the control treatment. No significant differences in citrate, α-lactalbumin, or protein content were observed between treatment groups. The most dramatic changes in secretion composition as a consequence of cabergoline treatment occurred during the first week of the dry period, when lactose concentrations and the citrate:lactoferrin molar ratio were lower and lactoferrin concentrations higher than in the control cows. Cabergoline treatment also tended to increase fat content and somatic cell count more rapidly following dry-off compared with the control group. These changes in mammary secretion composition following the abrupt cessation of lactation indicate that cabergoline treatment facilitated dry-off and effectively accelerated mammary gland involution.
Topics: Animals; Cabergoline; Cattle; Cell Count; Ergolines; Female; Lactation; Mammary Glands, Animal; Milk; Prolactin
PubMed: 27179868
DOI: 10.3168/jds.2015-10782 -
Journal of Neuroendocrinology Mar 2012In the female rat, a complex interplay of both stimulatory and inhibitory hypothalamic factors controls the secretion of prolactin. Prolactin regulates a large number of...
In the female rat, a complex interplay of both stimulatory and inhibitory hypothalamic factors controls the secretion of prolactin. Prolactin regulates a large number of physiological processes from immunity to stress. Here, we have chosen to focus on the control of prolactin secretion in the female rat in response to suckling, mating and ovarian steroids. In all three of these states, dopamine, released from neurones in the mediobasal hypothalamus, is a potent inhibitory signal regulating prolactin secretion. Early research has determined that the relief of dopaminergic tone is not sufficent to account for the full surge of prolactin secretion observed in response to the suckling stimulus, launching a search for possible prolactin-releasing factors. This research has subsequently broadened to include searching for prolactin-releasing factors controlling prolactin secretion after mating or ovarian steroids. A great deal of literature has suggested that this prolactin-releasing factor may include oxytocin. Oxytocin receptors are present on lactotrophs. These oxytocin receptors respond to exogenous oxytocin and antagonism of endogenous oxytocin inhibits lactotroph activity. In addition, the pattern of oxytocin neuronal activity and oxytocin release correlate with the release of prolactin. Here, we suggest not only that oxytocin is stimulating prolactin secretion, but also that prolactin secretion is controlled by a complex network of positive (oxytocin) and negative (dopamine) feedback loops. We discuss the available literature and attempt to describe the circuitry we believe may be responsible for controlling prolactin secretion.
Topics: Animals; Animals, Suckling; Dopamine; Female; Neurons; Oxytocin; Prolactin; Rats
PubMed: 22129099
DOI: 10.1111/j.1365-2826.2011.02263.x -
Proceedings of the National Academy of... Jul 2019Dopamine neurons of the hypothalamic arcuate nucleus (ARC) tonically inhibit the release of the protein hormone prolactin from lactotropic cells in the anterior...
Dopamine neurons of the hypothalamic arcuate nucleus (ARC) tonically inhibit the release of the protein hormone prolactin from lactotropic cells in the anterior pituitary gland and thus play a central role in prolactin homeostasis of the body. Prolactin, in turn, orchestrates numerous important biological functions such as maternal behavior, reproduction, and sexual arousal. Here, we identify the canonical transient receptor potential channel Trpc5 as an essential requirement for normal function of dopamine ARC neurons and prolactin homeostasis. By analyzing female mice carrying targeted mutations in the gene including a conditional Trpc5 deletion, we show that Trpc5 is required for maintaining highly stereotyped infraslow membrane potential oscillations of dopamine ARC neurons. Trpc5 is also required for eliciting prolactin-evoked tonic plateau potentials in these neurons that are part of a regulatory feedback circuit. Trpc5 mutant females show severe prolactin deficiency or hypoprolactinemia that is associated with irregular reproductive cyclicity, gonadotropin imbalance, and impaired reproductive capabilities. These results reveal a previously unknown role for the cation channel Trpc5 in prolactin homeostasis of female mice and provide strategies to explore the genetic basis of reproductive disorders and other malfunctions associated with defective prolactin regulation in humans.
Topics: Animals; Arcuate Nucleus of Hypothalamus; Arousal; Dopaminergic Neurons; Feedback, Physiological; Female; Gene Expression Regulation; Genetic Diseases, Inborn; Gonadotropins; Homeostasis; Humans; Lactation Disorders; Membrane Potentials; Mice; Mutation; Prolactin; Reproduction; Signal Transduction; TRPC Cation Channels
PubMed: 31285329
DOI: 10.1073/pnas.1905705116 -
Reproduction, Nutrition, Development 1990The effect of L-DOPA on milk removal and on prolactin release during suckling or milking was studied in lactating ewes. Various doses of L-DOPA (25, 50, 100 and 200 mg...
The effect of L-DOPA on milk removal and on prolactin release during suckling or milking was studied in lactating ewes. Various doses of L-DOPA (25, 50, 100 and 200 mg per animal) were injected iv 30 min before the suckling or milking period. Control ewes were injected with 0.9% NaCl solution only. Milking induced a significant long-lasting release of prolactin. An inhibition of milk removal was obtained with the dose of 200 mg of L-DOPA. An inhibition of prolactin secretion was observed related to the dose of drug administered. The inhibitory effect of 200 mg of L-DOPA on the secretion of prolactin after milking lasted for about 120 min, and thereafter a significant increase in serum prolactin level occurred. This increase in serum prolactin was not due to a "rebound" effect of L-DOPA, since the milking stimulus had to be present to induce the delayed increase in prolactin. Doses of 25 or 50 mg of L-DOPA prevented the surge of prolactin observed immediately after milking, but a long-lasting release of prolactin was obtained thereafter. The inhibitory effect of L-DOPA on prolactin release could be overridden by the suckling or milking stimuli according to the dose administered. The suckling stimulus was more effective than milking in overriding the inhibitory effect of the low dose of L-DOPA. The results indicate that milk removal and prolactin release induced by milking or suckling in lactating ewes is inhibited by an increase in monoamines at the hypothalamic-hypophyseal level.
Topics: Animals; Dose-Response Relationship, Drug; Female; Kinetics; Lactation; Levodopa; Prolactin; Sheep
PubMed: 2291808
DOI: 10.1051/rnd:19900505 -
Anatomical Record (Hoboken, N.J. : 2007) Jul 2007This work deals with the quantification of serotonin-immunoreactive prostate neuroendocrine cells (NECs) in rats exposed to prolactin in normal, cyproterone...
Effect of prolactin and bromocriptine on the population of prostate neuroendocrine cells from intact and cyproterone acetate-treated rats: stereological and immunohistochemical study.
This work deals with the quantification of serotonin-immunoreactive prostate neuroendocrine cells (NECs) in rats exposed to prolactin in normal, cyproterone acetate-exposed, and bromocriptine-exposed animals to establish the possible influence of prolactin with or without androgenic blockade on this cell population. Thirty male peripubertal Sprague-Dawley rats were grouped as controls (CT) and those treated with cyproterone acetate (CA), cyproterone acetate plus prolactin, cyproterone acetate plus bromocriptine, prolactin (PL), and bromocriptine (BC). The volume of ductal epithelium (Vep) and total number (NSER) of the NECs serotonin-immunoreactive were measured. NECs were detected in the periurethral ducts. Compared to CT, Vep was increased in PL and BC and NSER was decreased in CA and increased in the prolactin or bromocriptine groups. The androgenic blockade decreases NSER in rat prostate; PL induces in normal and cyproterone acetate-treated rats the increase of NSER; and BC exerts a local effect over the prostate similar to that described for PL.
Topics: Androgen Antagonists; Animals; Bromocriptine; Castration; Cell Count; Cell Shape; Cell Size; Cyproterone Acetate; Epithelial Cells; Hormone Antagonists; Male; Neurosecretory Systems; Prolactin; Prostate; Rats; Rats, Sprague-Dawley; Serotonin
PubMed: 17541972
DOI: 10.1002/ar.20552 -
Molecular Endocrinology (Baltimore, Md.) May 2015Adult stem/progenitor cells are found in many tissues, where their primary role is to maintain homeostasis. Recent studies have evaluated the regulation of adult... (Review)
Review
Adult stem/progenitor cells are found in many tissues, where their primary role is to maintain homeostasis. Recent studies have evaluated the regulation of adult stem/progenitor cells by prolactin in various target tissues or cell types, including the mammary gland, the prostate, the brain, the bone marrow, the hair follicle, and colon cancer cells. Depending on the tissue, prolactin can either maintain stem cell quiescence or, in contrast, promote stem/progenitor cell expansion and push their progeny towards differentiation. In many instances, whether these effects are direct or involve paracrine regulators remains debated. This minireview aims to overview the current knowledge in the field.
Topics: Adult Stem Cells; Animals; Cell Differentiation; Cell Self Renewal; Humans; Prolactin; Signal Transduction
PubMed: 25793405
DOI: 10.1210/me.2015-1022 -
British Medical Journal Apr 1979
Topics: Female; Humans; Premenstrual Syndrome; Prolactin
PubMed: 571305
DOI: 10.1136/bmj.1.6168.954 -
British Medical Journal Oct 1972
Topics: Adult; Female; Hemangioma; Humans; Infant, Newborn; Male; Obstetric Labor, Premature; Placenta; Placenta Diseases; Pregnancy; Prolactin
PubMed: 5082566
DOI: 10.1136/bmj.4.5834.233-c -
British Medical Journal Jul 1971
Topics: Animals; Female; Gynecomastia; Histocytochemistry; Humans; Lactation Disorders; Male; Pituitary Gland; Pregnancy; Prolactin; Rabbits
PubMed: 5559038
DOI: No ID Found