Corticotropin-releasing hormone regulation of immunoreactive beta-endorphin secretion in Leydig cells in the rat testis.
Item
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Title
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Corticotropin-releasing hormone regulation of immunoreactive beta-endorphin secretion in Leydig cells in the rat testis.
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Identifier
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AAI9119627
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identifier
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9119627
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Creator
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Eskeland, Nahida Lucia.
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Contributor
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Adviser: Beth S. Schachter
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Date
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1991
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Language
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English
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Publisher
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City University of New York.
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Subject
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Health Sciences, Pharmacology
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Abstract
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Corticotropin-releasing hormone (CRH), a hypothalmic peptide, is the principal stimulator of pro-opiomelanocortin (POMC) synthesis and secretion in the pituitary gland. POMC and CRH syntheses have been documented in other tissues such as the testis, but a possible regulatory action of CRH on POMC in the testis was unknown. Therefore the current study evaluated various aspects of CRH action on POMC peptide secretion from testicular cells. CRH stimulated secretion of {dollar}\beta{dollar}-endorphin ({dollar}\beta{dollar}EP, a POMC peptide) from a subset population of Leydig cells in culture. The secretagogue acted in a dose-dependent fashion and was inhibited by a CRH competitive antagonist, demonstrating that POMC-producing Leydig cells have functional CRH receptors. Moreover, we have shown that CRH stimulated ir{dollar}\beta{dollar}EP levels in testicular interstitial fluid in the intact testis of pubertal but not adult rats. These data suggest a physiological and developmental function for CRH in the testis.;Only short POMC-like transcripts that are missing the amino terminal signal-peptide coding region have been reported in the rat testis. Using polymerase chain reaction, a full length pituitary-like POMC mRNA was detected in the rat testis, showing that the rat testis has a POMC transcript capable of encoding a prohormone that can go through processing, packaging and secretion pathway for regulated secretory peptides.;The effect of two physiologically relevant temperatures on the CRH/POMC system was analyzed since testicular function is known to be sensitive to thermal changes. At 34{dollar}\sp\circ{dollar}C, CRH dose-response curves for both TM3 (a mouse Leydig cell-line) and AtT20 (a mouse pituitary cell-line) had significantly lower EC{dollar}\sb{lcub}50{rcub}{dollar}s than at 37{dollar}\sp\circ{dollar}C. These studies suggest that CRH receptors or post receptor mechanisms may be sensitive to temperature changes.;Finally, possible source(s) of CRH synthesis in the rat testis was investigated. Using non-radioactive in situ hybridization on adult testis sections, CRH mRNA was detected predominantly in germ cells, suggesting that these cells may be a major source of CRH.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
