title: Alpha-melanocyte-stimulating hormone stimulates prolactin secretion through melanocortin-3 receptors expressed in mammotropes in the mouse pituitary.
abstract: 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 alpha-melanocyte-stimulating hormone (alpha-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 alpha-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. alpha-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 alpha-MSH stimulates PRL release and proliferation of mammotropes through MC3-Rs, and suggest that alpha-MSH from intermediate lobes can regulate mammotrope functions in the mouse pituitary.
authors.affiliation: Department of Biology, Faculty of Science, Faculty of Agriculture, Okayama University, Okayama, Japan.
authors.forename: Ryusei
authors.initials: R
authors.lastname: Matsumura
authors.forename: Chika
authors.initials: C
authors.lastname: Takagi
authors.forename: Tomoshi
authors.initials: T
authors.lastname: Kakeya
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Okuda
authors.forename: Sakae
authors.initials: S
authors.lastname: Takeuchi
authors.forename: Sumio
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D001973:Bromodeoxyuridine / Q000378:metabolism; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D013006:Growth Hormone / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D051379:Mice; D008813:Mice, Inbred ICR; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D011838:Radiation-Sensitizing Agents / Q000378:metabolism; D044104:Receptor, Melanocortin, Type 3; D018043:Receptors, Corticotropin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012727:Sex Characteristics; D013997:Time Factors; D000521:alpha-MSH / Q000494:pharmacology*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D011838:Radiation-Sensitizing Agents; D044104:Receptor, Melanocortin, Type 3; D018043:Receptors, Corticotropin; C103272:SHU 9119; D000521:alpha-MSH; D011388:Prolactin; D013006:Growth Hormone; D009074:Melanocyte-Stimulating Hormones; D001973:Bromodeoxyuridine