Regulation of melanophore responsiveness in the background-adapted medaka, Oryzias latipes: change in the intracellular signaling system.
The responsiveness of melanophores of the medaka fish (wild type, Oryzias latipes) to a neurotransmitter and hormones is changed differentially after long-term adaptation to a black or white background. In the present study, we further examined whether this phenomenon involved some change in the intracellular signaling system. Using a permeabilized melanophore model, in which pigment granules could be dispersed by exogenously applied cAMP, the requirement of cAMP for pigment-dispersing reaction was revealed to be higher in melanophores of fish adapted to a black background (B cells) than in those of white background-adapted fish (W cells). Specific inhibitors of cAMP-dependent protein kinase (PKA) and cyclic nucleotide phosphodiesterase did not reduce the difference in the pigment dispersion level between B and W cells. A similar result was obtained with the free catalytic subunit of PKA. In contrast, the inhibition of protein phosphatase activity by okadaic acid diminished the difference in the responsiveness between B and W cells. These results suggest that the activity of protein phosphatase in B cell is higher than that in W cells, and that the change in the melanophore responsiveness by long-term chromatic adaptation to a background involves the change in the enzyme activity in the intracellular signaling system.
Sugimoto
M
M
Department of Biomolecular Science, Faculty of Science, Toho University, Chiba, Japan. sugimoto@biomol.sci.toho-u.ac.jp
Nagamori
H
H
Yasui
H
H
Oshima
N
N
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D007546:Isoquinolines / Q000494:pharmacology; D008547:Melanophores / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D009990:Oryzias; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010860:Pigments, Biological / Q000378:metabolism*; D015398:Signal Transduction; D013449:Sulfonamides; D000521:alpha-MSH / Q000494:pharmacology
D007546:Isoquinolines; D010726:Phosphodiesterase Inhibitors; D010860:Pigments, Biological; D013449:Sulfonamides; D019319:Okadaic Acid; D000521:alpha-MSH; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D015056:1-Methyl-3-isobutylxanthine