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      α-Melanocyte-Stimulating Hormone Stimulates Prolactin Secretion through Melanocortin-3 Receptors Expressed in Mammotropes in the Mouse Pituitary

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          The intermediate lobe of rodent pituitaries is involved in the regulation of prolactin (PRL) secretion from the anterior lobe. In a previous study, we demonstrated the stimulatory effect of α-melanocyte-stimulating hormone (α-MSH) on PRL release and the expression of melanocortin-3 receptors (MC3-Rs) in cultured mouse pituitary cells. The aim of the present study was to clarify whether α-MSH directly stimulates PRL release through the MC3-Rs by determining the cell type of MC3-R-expressing cells in the mouse pituitary anterior lobe. Northern blot analysis revealed a 2.7-kb transcript for MC3-R mRNA in the anterior and neurointermediate lobes of pituitary glands of adult male and female mice. Dual cellular localization of MC3-R mRNA and PRL or growth hormone (GH) in the mouse pituitary glands was performed by in situ hybridization analysis of MC3-R mRNA followed by immunocytochemical detection of PRL or GH. MC3-R mRNA was detected in most mammotropes and some somatotropes. α-MSH increased PRL release and stimulated DNA replication in mammotropes, and these effects were blocked by SHU9119, an antagonist of MC3-R and MC4-R. These results indicate that α-MSH stimulates PRL release and proliferation of mammotropes through MC3-Rs, and suggest that α-MSH from intermediate lobes can regulate mammotrope functions in the mouse pituitary.

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          Most cited references 6

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          Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction.

          A new method of total RNA isolation by a single extraction with an acid guanidinium thiocyanate-phenol-chloroform mixture is described. The method provides a pure preparation of undegraded RNA in high yield and can be completed within 4 h. It is particularly useful for processing large numbers of samples and for isolation of RNA from minute quantities of cells or tissue samples.
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            Intercellular Communication in the Anterior Pituitary

             J. Schwartz (2000)
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              Further pharmacological characterization of the selective melanocortin 4 receptor antagonist HS014: comparison with SHU9119.

              SHU9119 and HS014 are cyclic MSH analogues which are widely used to elucidate the physiology behind the various effects of the MSH peptides and their receptors. We carefully compared the potency of SHU9119 and HS014 in cells expressing the MC receptor clones. We found that both the peptides are partial agonists for the MC1 and MC5 receptors while they are potent antagonists for the MC3 and MC4 receptors. In agreement with earlier binding data, we found that SHU9119 has equal potency for the MC3 and MC4 receptor whereas HS014 has at least 10-fold higher potency for the MC4 receptor than the MC3 receptor in cAMP assay. Moreover, we synthesized analogues of HS014 where the C-terminal was truncated. We found that this C-terminal fragment of HS014, in particular the Lys(14), has a major influence on the affinity for the MC4 receptor without any particular influence on the affinity for the other MC receptors.

                Author and article information

                S. Karger AG
                August 2003
                20 August 2003
                : 78
                : 2
                : 96-104
                aDepartment of Biology, Faculty of Science, and bLaboratory of Reproductive Endocrinology, Faculty of Agriculture, Okayama University, Okayama, Japan
                71965 Neuroendocrinology 2003;78:96–104
                © 2003 S. Karger AG, Basel

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                Page count
                Figures: 5, References: 41, Pages: 9
                Gonadal Steroids and Regulation of Reproductive Hormones


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