Figure 2.

Wild type AQP1 channels show a dose-dependent ionic conductance response to the nitric oxide donor, sodium nitroprusside. A. Comparison of representative currents before and after 14 mM SNP in AQP1-expressing and control oocytes. Voltage steps were +60 mV to -110 mV in -10 mV intervals, from -40 mV holding potential. The net current is (final)-(initial). B. Dose-dependence of net current responses of wild type AQP1-expressing oocytes, with the same voltage protocol as in (A). C. Summary of data for conductance responses (mean ± SEM, n = 9–34 oocytes per group) at different doses of SNP (indicated in mM on horizontal axis). 'Initial' data are the conductance levels of the oocytes recorded prior to SNP application, and represent total conductance rather than net values. The net conductance responses were calculated by subtracting the matched initial values individually from the SNP response for each oocyte.D. Mean values ± SEM (n = 7 oocytes per group within the same batch of oocytes) are shown for net conductance responses to SNP for control (square) and AQP1-expressing oocytes (circle). The difference between mean net AQP1 and control conductances (diamond) was fit to estimate an EC₅₀ value of 7.8 mM SNP; see text for details. E. Dose-dependent rate of activation of ionic current by SNP in representative AQP1-expressing oocytes, measured at 5 sec intervals with voltage steps to +40 mV from a holding potential of -40 mV. The arrow indicates the time of application of SNP in the recording chamber bath. Data prior to the application are superimposed.