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Figure 9. Function of G99R in 150 mM Na+o, with FXYD1 and at 34°C. (A) Continuous recording at −50 mV from an oocyte injected with G99R in which increasing K+o concentrations are applied in the presence of 150 mM Na+o (K0.5-V plotted in Fig. 8). The ouabain-sensitive currents in Na+o elicited by voltage pulses from −180 to 40 mV, in 20-mV increments, are shown in high temporal resolution in the center. The Q-V curve from those transient currents are shown on the right and was fitted with a Boltzmann distribution (line plot) with parameters Qtot = 33.4 nC, V1/2 = −108 mV, and k = 53 mV. All eight oocytes gave comparable results with inward currents absent from recordings. (B) Current at −50 mV from an oocyte injected with α1-G99Rβ1FXYD1 to which increasing K+o concentrations were applied in the 125 mM Na+o. The transient currents elicited are shown in the center and the Q-V curve from those transient currents are on the right. The Boltzmann distribution (fitted line plot) had parameters Qtot = 12.1 nC, V1/2= −136 mV, and k= 77 mV. Note that despite robust expression demonstrated by a large Qtot, the total pump current is largely reduced compared with G99R without FXYD1, even at 20 mM K+o. Three oocytes gave similar results with lower pump currents than non-FXYD1 coinjected oocytes. (C) Recording at −50 mV from an oocyte injected with G99R in which application of 5 mM K+o in 125 mM Na+o was performed at 24°C and then at 34°C. Note absence of significant inward current upon application of ouabain, despite deterioration of the oocyte. Three oocytes gave nearly identical results. Image published in: Meyer DJ et al. (2017) © 2017 Meyer et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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