Electrogenicity of the Na-K-ATPase pump in bullfrog cornea epithelium.
The effect of changing the K concentration in the aqueous solution was studied in the frog cornea. In general, when the K concentration was increased from 4 to 20 or 79 mM, the transepithelial PD and resistance decreased. If K was decreased from 79 to 4, 20 to 4, or 4 to 0 mM, or any other combination, the PD and resistance increased. These are normal PD responses. If after a K-free period of more than 5-10 min the K was increased to 4 mM, the PD increased, an anomalous PD response. If K was increased from 0 to 20 mM, there was an initial PD increase (anomalous response) followed by a PD decrease (normal response). If K was increased from 0 to 79 mM the PD decreased, normal response only. The resistance decreased with every increase in K concentration. Anomalous responses were abolished in Na-free solutions and in the presence of both 10(-3) M ouabain and 10(-4) M vanadate in the aqueous solution. We interpret the results on the basis of two pathways, a simple K-conductive pathway and an electrogenic Na-K-ATPase pump pathway with more Na's than K's per cycle. The normal or anomalous PD responses to changes in aqueous K concentration depend on the relative resistance of the two pathways.
Carrasquer
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Ahn
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Schwartz
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Rehm
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D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003315:Cornea / Q000201:enzymology* / Q000502:physiology; D004848:Epithelium / Q000201:enzymology / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011892:Rana catesbeiana; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
D014639:Vanadium; D014638:Vanadates; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium