title: Pigment-dispersing activities and cortisol-releasing activities of melanocortins and their receptors in xanthophores and head kidneys of the goldfish Carassius auratus.
abstract: The five subtypes of melanocortin receptors (MCRs) mediate the functions of α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH). In fish, these hormones are involved in pigment dispersion and cortisol release, respectively. α-MSH-related peptides exhibit ACTH-like activity in certain fishes. We recently found that multiple Mcr transcripts are expressed in some cell types in the barfin flounder, which is related to regulation of α-MSH activities. Similar results were also observed for the cortisol-releasing activity of α-MSH-related peptides in the head kidney. The present study was undertaken to assess relationship between the expression of multiply expressed Mcrs and α-MSH activities using goldfish. We also determined if α-MSH-related peptides exhibit ACTH-like activity in goldfish. The transcripts of Mc1r, but not those of other subtypes, were observed in xanthophores. α-MSH, which has an acetyl group at the N-terminus, was found to disperse pigment in a dose-dependent manner in xanthophores. This potency was found to be slightly greater than that of desacetyl-α-MSH. These results support our findings that MCR has a higher affinity for α-MSH when single Mcr subtype is expressed. On the other hand, transcripts of Mc2r, but not those of other subtypes, were observed in the head kidney. ACTH(1-24)-stimulated cortisol release was observed in a dose-dependent manner, while α-MSH-related peptides showed no activity. It therefore appears that MC2R also acts as an ACTH-specific receptor in goldfish and that association of α-MSH-related peptides upon release of cortisol is uncommon in fishes.
authors.affiliation: School of Marin Biosciences, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Chiba
authors.forename: Kanta
authors.initials: K
authors.lastname: Mizusawa
authors.forename: Nobuo
authors.initials: N
authors.lastname: Suzuki
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Cerdá-Reverter
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D058500:Animal Fins / Q000378:metabolism; D000818:Animals; D006054:Goldfish / Q000378:metabolism*; D060226:Head Kidney / Q000378:metabolism*; D006854:Hydrocortisone / Q000378:metabolism; D053486:Melanocortins / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D010860:Pigments, Biological / Q000032:analysis / Q000378:metabolism*; D044101:Receptors, Melanocortin / Q000737:chemistry / Q000502:physiology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012867:Skin / Q000378:metabolism
chemical_list: D053486:Melanocortins; D010860:Pigments, Biological; D044101:Receptors, Melanocortin; D006854:Hydrocortisone