title: Mechanism by which an elevation of extracellular glucide concentration induces pigment aggregation in medaka melanophores.
abstract: An increase in glucide concentration induces pigment aggregation in melanophores in the skin on scales isolated from the medaka, Oryzias latipes. In this study, hexoses (including the common D-isomers of glucose, galactose, fructose, and mannitol) were examined. Denervated melanophores were refractory to such stimuli. An alpha-adrenolytic agent, phentolamine, effectively blocked the responses of normally innervated melanophores. The pigment-aggregating action of glucide was inhibited by withdrawal of Ca(2+) and Mg(2+) ions from the medium. A specific blocker of voltage-dependent N-type Ca(2+) channels, the omega-conotoxin GVIA, also inhibited the glucide action. The conclusion derived is that an elevation of glucide levels acts to open Ca(2+) channels of presynaptic membranes of sympathetic postganglionic fibers, and the consequently released adrenergic transmitter acts on the effector cells to induce the aggregation of their pigmentary organelles.
authors.affiliation: Department of Biomolecular Science, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan.
authors.forename: Ryozo
authors.initials: R
authors.lastname: Fujii
authors.forename: Makoto
authors.initials: M
authors.lastname: Goda
authors.forename: Noriko
authors.initials: N
authors.lastname: Oshima
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D015220:Calcium Channels; D003714:Denervation; D005260:Female; D006601:Hexoses / Q000494:pharmacology*; D008297:Male; D008543:Melanins / Q000378:metabolism*; D008547:Melanophores / Q000187:drug effects* / Q000378:metabolism; D020460:Melanosomes / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D009990:Oryzias / Q000033:anatomy & histology / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D012880:Skin Pigmentation / Q000187:drug effects*
chemical_list: D000317:Adrenergic alpha-Antagonists; D015220:Calcium Channels; D006601:Hexoses; D008543:Melanins; D010646:Phentolamine