Mechanism by which an elevation of extracellular glucide concentration induces pigment aggregation in medaka melanophores.
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.
Fujii
Ryozo
R
Department of Biomolecular Science, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan.
Goda
Makoto
M
Oshima
Noriko
N
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*
D000317:Adrenergic alpha-Antagonists; D015220:Calcium Channels; D006601:Hexoses; D008543:Melanins; D010646:Phentolamine