無K^+液中におけるラット骨格筋の起電性Naポンプ

概要

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The time course of changes in resting potential following the removal of K^+ from Krebs solution was studied in the isolated rat soleus muscle. In K^+-free Krebs solution the muscle fibers hyperpolarized to a peak within 60 min, followed by a variable in gradual depolarization over the next few hours. A significant decrease of the intracellular K^+ concentration ([K^+]_i) occurred within 30 min in K^+-free Krebs. Compensatory increase of the intracellular Na^+ concentration ([Na^+]_i) lagged behind [K^+]_i change. Both hyperpolarization and successive depolarization in K^+-free medium were modified with varying [Na^+]_0, [Ca^<2+>]_0 or osmotic strength. A part of the hyperpolarization was reduced by adding ouabain. Therefore, ouabain-sensitive potential of the fibers in K^+-free medium was attributed to the activation of electrogenic Na-pump by K^+ leaked out continuously from the fibers and accumlated just outside of cell membrane, but not to changes of membrane Na^+ and Cl^- permeabilities. It is concluded that hyperpolarization of muscles exposed to K^+-free medium is the sum of the diffusional K^+ potential and ouabain-sensitive metabolic potential. Interestingly, the time course of changes of membrane response to K^+-free Krebs was identical between companion soleus muscles in the same rat, though it varied among different rats.
熊本保健科学大学の論文
1983-01-15