Summary
We have studied current (I Str) through the Na, K pump in amphibian oocytes under conditions designed to minimize parallel undesired currents. Specifically,I Str was measured as the strophanthidin-sensitive current in the presence of Ba2−, Cd2+ and gluconate (in place of external Cl−). In addition,I Str was studied only after the difference currents from successive applications and washouts of strophanthidin (Str) were reproducible. The dose-response relationship to Str in four oocytes displayed a meanK 0.5 of 0.4 μm, with 2–5 μm producing 84–93% pump' block. From baseline data with 12 Na+-preloaded oocytes, voltage clamped in the range [−170, +50 mV] with and without 2–5 μm Str, the averageI Str depended directly onV m up to a plateau at 0 mV with interpolated zero current at −165 mV. In three oocytes, lowering the external [Na+] markedly decreased the voltage sensitivity ofI p , while producing only a small change in the maximal outwardI Str. In contrast, decreasing the external [K+] from 25 to 2.5mm reducedI Str at 0 mV without substantially affecting its voltage dependence. At K+ concentrations of ≤1mm, both the absolute value ofI Str at 0 mV and the slope conductance were reduced. In eight oocytes, the activation of the averagedI Str by [K+] o over the voltage interval [−30, +30 mV] was well fit by the Hill equation, with K′=1.7±0.4mm andnH (the minimum number of K+ binding sites) =1.7±0.4. The results unequivocally establish that the cardiotonic-sensitive current ofRana oocytes displays only a positive slope conductance for [K+] o >1mm. There is therefore no need to postulate more than one voltage-sensitive step in the cycling of the Na, K pump under physiologic conditions. The effects of varying external Na+ and K+ are consistent with results obtained in other tissues and may reflect an ion-well effect.
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References
Albers, R.W., Koval, G.J., Siegel, G.J. 1968. Studies on the interaction of ouabain and other cardioactive steroids with Na,K-activated ATPase.Mol. Pharmacol. 4:324–336
Bahinski, A., Nakao, M., Gadsby, D.C. 1988. Potassium translocation by the Na+/K+ pump is voltage insensitive.Proc. Natl. Acad. Sci. USA 85:3412–3416
Barish, M.E. 1983. A transient calcium-dependent chloride current in the immatureXenopus oocyte.J. Physiol. 342:309–325
Béhé, P., Turin, L. 1984. Arrest and reversal of the electrogenic sodium pump under voltage clamp. Proceedings of the 8th International Biophysical Congress (Bristol, U.K.) p. 304
Bezanilla, F. 1985. A high capacity data recording device based on a digital audio processor and a video cassette recorder.Biophys. J. 47:437–441
Borlinghaus, R., Apell, H.-J., Läuger, P. 1987. Fast charge translocations associated with partial reactions of the Na,K-pump: I. Current and voltage transients after photochemical release of ATP.J. Membrane Biol. 97:161–178
Civan, M.M. 1983. Epithelial Ions and Transport. Application of Biophysical Techniques. Wiley Interscience. New York
Civan, M.M., Bookman, R.J. 1982. Transepithelial Na+ transport and the intracellular fluids: A computer study.J. Membrane Biol. 65:63–80
Civan, M.M., Peterson-Yantorno, K., George, K., O'Brien, T.G. 1989. Interactions of TPA and insulin on Na+ transport across frog skin.Am. J. Physiol. 256:C569-C578
Cross, N.L. 1981. Initiation of the activation potential by an increase in intracellular calcium in eggs of the frog,Rana pipiens.Dev. Biol. 85:380–384
De Weer, P., Gadsby, D.C., Rakowski, R.F. 1988. Voltage dependence of the Na−K pump.Annu. Rev. Physiol. 50:225–241
Eisner, D.A., Valdeolmillos, M., Wray, S. 1987. The effects of membrane potential on active and passive sodium transport inXenopus oocytes.J. Physiol. 385:643–659
Fendler, K., Grell, E., Bamberg, E. 1987. Kinetics of pump currents generated by the Na+K+-ATPase.FEBS Lett. 224:83–88
Forbush, B., III 1983. Cardiotonic steroid binding to Na,K-ATPase.In: Current Topics in Membranes and Transport. J.F. Hoffman and B. Forbush III, editors) Vol. 19. pp. 167–201. Academic Press, New York
Gadsby, D.C., Kimura, J., Noma, A. 1985. Voltage dependence of Na/K pump current in isolated heart cells.Nature 315:63–65
Gadsby, D.C., Nakao, M. 1987. [Na] dependence of the Na/K pump current-voltage relationship in isolated cells from guinea-pig ventricle.J. Physiol. 382: 106P
Gadsby, D.C., Nakao, M., 1989. Steady-state current-voltage relationship of the Na/K pump in guinea pig ventricular myocytes.J. Gen. Physiol. 94:511–537
Glynn, I.M. 1984. The electrogenic sodium pumps.In: Electrogenic Transport: Fundamental Principles and Physiological Implications. M.P. Blaustein and M. Lieberman, editors. pp. 33–48. Raven, New York
Goldshlegger, R., Karlish, S.J.D., Raphaeli, A., Stein, W.D. 1987. The effect of membrane potential on the mammalian sodium-potassium pump reconstituted into phospholipid vesicles.J. Physiol. 387:331–355
Hagiwara, S., Jaffe, L.A. 1979. Electrical properties of egg cell membranes.Annu. Rev. Biophys. Bioeng. 8:385–416
Hagiwara, S., Miyazaki, S., Rosenthal, N.P. 1976. Potassium current and the effect on this current during anomalous rectification of the egg cell membrane of a starfish.J. Gen. Physiol. 67:621–638
Hagiwara, S., Takahashi, K. 1967. Surface density of calcium ion and calcium spikes in the barnacle muscle fiber membrane.J. Gen. Physiol. 50:583–601
Koefoed-Johnsen, V., Ussing, H.H. 1958. The nature of the frog skin potential.Acta Physiol. Scand. 42:298–308
Lafaire, A.V., Schwarz, W. 1986. Voltage dependence of the rheogenic Na+/K+ ATPase in the membrane of oocytes ofXenopus laevis.J. Membrane biol. 91:43–51
Läuger, P. 1990. Kinetic basis of voltage sensitivity.J. Gen. Physiol. (in press)
Läuger, P., Apell, H.-J. 1986. A microscopic model for the current-voltage behaviour of the Na,K-pump.Eur. Biophys. J. 13:309–321
Lew, V.L., Ferreira, H.G., Moura, T. 1979. The behaviour of transporting epithelial cells. I. Computer analysis of a basic model.Proc. R. Soc. London B. 206:53–83
Lindemann, B. 1979. The minimal information content ofE oNa .Colloq. Inst. Natl. Santé Rech. Med. 85:241–252
Marx, A., Ruppersberg, J.P., Rudel, R. 1987. Dependence of the electrogenic pump current ofXenopus oocytes on external potassium.Pfluegers Arch. 408:537–539
Masui, Y. 1967. Relative roles of the pituitary, follicle cells and progesterone in the induction of oocyte maturation inRana pipiens.J. Exp. Zool. 117:365–376
Miledi, R., Parker, I. 1984. Chloride current induced by injection of calcium intoXenopus oocytes.J. Physiol. 357:173–183
Nagel, W., Pope, M.B., Peterson, K., Civan, M.M. 1980. Electrophysiologic changes associated with potassium depletion of frog skin.J. Membrane Biol. 57:235–241
Nakao, M., Gadsby, D.C. 1986. Voltage dependence of Na translocation by the Na/K pump.Nature 323:628–630
Nakao, M., Gadsby, D.C. 1989. [Na] and [K] dependence of the Na/K pump current-voltage relationship in guinea pig ventricular myocytes.J. Gen. Physiol. 94:539–565
Post, R.L., Kume, S., Tobin, T., Orcutt, B., Sen, A.K. 1969. Flexibility of an active center in sodium-plus-potassium adenosine triphosphatase.J. Gen. Physiol. 54:306s-326s
Rakowski, R.F., Gadsby, D.C., De Weer, P. 1989. Stoichiometry and voltage dependence of the sodium pump in voltage-clamped, internally dialyzed squid giant axon.J. Gen. Physiol. 93:903–941
Rakowski, R.F., Paxson, C.L. 1988. Voltage dependence of Na/K pump current inXenopus oocytes.J. Membrane Biol. 106:173–182
Rakowski, R.F., Vasilets, L.A., Schwarz, W. 1990. Conditions for a negative slope in the current-voltage relationship of the Na/K pump inXenopus oocytes.Biophys. J. 57:182a
Richter, H.-P., Jung, D., Passow, H. 1984. Regulatory changes of membrane transport and ouabain binding during progesterone-induced maturation ofXenopus oocytes.J. Membrane Biol. 79:203–210
Schweigert, B., Lafaire, A.V., Schwarz, W. 1988. Voltage dependence of the Na−K ATPase: Measurements of ouabain-dependent membrane current and ouabain binding in oocytes ofXenopus laevis.Pfluegers Arch. 412:579–588
Skou, J.C. 1957. The influence of some ions on the adenosine triphosphatase from peripheral nerves.Biochim. Biophys. Acta 23:394–401
Stimers, J.R., Shigeto, N., Lieberman, M. 1990. Intracellular sodium affects ouabain interaction with the Na/K pump in cultured chick cardiac myocytes.J. Gen. Physiol. 95:61–76
Weinstein, S.P., Kostellow, A.B., Ziegler, D.H., Morrill, G.A. 1982. Progesterone-induced down-regulation of an electrogenic Na+, K+-ATPase during the first meiotic division in amphibian oocytes.J. Membrane Biol. 69:41–48
Wu, M.M., Civan, M.M. 1988. Voltage-dependence of strophanthidin-sensitive current ofRana oocytes.Biophys. J. 53:139a
Wu, M.M., Civan, M.M. 1989. Voltage-dependence of the Na/K-pump ofRana oocytes.J. Gen. Physiol. 94:16a-17a
Wu, M.M., Civan, M.M. 1990. Voltage-dependence of the Na/K pump current ofRana oocytes.Biophys. J. 57:353a
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Wu, M.M., Civan, M.M. Voltage dependence of current through the Na,K-exchange pump ofRana oocytes. J. Membrain Biol. 121, 23–36 (1991). https://doi.org/10.1007/BF01870648
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DOI: https://doi.org/10.1007/BF01870648