Involvement of Ca^<2+> in the Direct Effect of K^+ on Xanthophores of the Medaka, Oryzias latipes(Physiology)

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The direct effect of K^+ on xanthophores of the medaka, Oryzias latipes, was studied using denervated scale preparations and cultured cells. At concentrations of 30 mM or higher, K^+ ions caused almost complete aggregation of pigment in denervated xanthophores. The withdrawal of divalent cations from the perfusing solution, or the addition of Ca^<2+> channel blocker to the medium, made the cells unresponsive to K^+. When Fluo 3-loaded xanthophores were stimulated by K^+, a temporary increase in the fluorescence intensity was observed. Experimental elevation of cytosolic Ca^<2+> concentration induced aggregation of pigment in denervated xanthophores pretreated with A23187. Forskolin, an activator of adenylate cyclase, inhibited the K^+-induced aggregation of pigment in a dose-dependent manner, whereas W-7, a calmodulin antagonist, did not. From these results, it is likely that membrane depolarization caused by elevated K^+ concentration in the perfusing medium may be accompanied by Ca^<2+> entry into the cytoplasm through volt-age-dependent Ca^<2+> channels present in the xanthophore membrane. This would result in inhibition of adenylate cyclase activity, since it is well established that decreases in intracellular cAMP level induce pigment aggregation in fish chromatophores.
社団法人日本動物学会の論文
1998-10-15