Rapid resting ion fluxes in goldfish hair cells are balanced by (Na+,K+)-ATPase.
Inhibition of sodium/potassium pumping by isolated goldfish hair cells led to a rapid gain of sodium and loss of potassium. Half-times for turnover were about 10 min, among the fastest of any cell type examined by electron-probe analysis. Pumping was inhibited by removal of extracellular potassium or by treatment with 1 mM ouabain, as expected of a classical (Na+,K+)-ATPase. The initial rate of entry of sodium after inhibition, about 4 mM/min, provided an estimate of resting sodium-entry and sodium-pumping rates. After return to control medium, cells loaded with sodium by removal of extracellular potassium could recover their normal high-potassium/low-sodium status. The initial rate of recovery (an estimate of the cells' maximum sodium-pumping rate) was sufficient to lower cell sodium by 10 mM/min. This functional estimate of hair-cell (Na+,K+)-ATPase activity was of the same order of magnitude as the biochemical activity of (Na+,K+)-ATPase previously reported for sensory epithelia of other species. The balance between sodium entry and sodium pumping determines hair-cell ionic composition, and thus the resting potential and the driving forces for sodium-coupled transport processes. Imbalance due to excess sodium entry or loss of pump capacity could have significant consequences for hair-cell function and integrity.
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Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston 02114.
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Lechene
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002712:Chlorides / Q000378:metabolism; D006054:Goldfish / Q000378:metabolism*; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D066298:In Vitro Techniques; D017136:Ion Transport; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
D002712:Chlorides; D010042:Ouabain; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase