Figure 4.

Nitrate-induced currents in Xenopus oocytes expressing GmN70. Oocytes were injected with GmN70 cRNA and were cultured for 4 d prior to two-electrode voltage clamp recording as described in “Materials and Methods.” A, Current records from a GmN70-injected oocyte bathed in 100 mm NaNO₃ or 100 mm sodium gluconate in the presence of standard recording-bath solution. The plot represents the currents obtained from a step-wise voltage protocol in which oocytes were recorded at V_m clamped from +60 to −80 mV in 20-mV increments. Each potential was maintained for 1 s with a 0.5-s recovery period at a holding potential of −35 mV between each voltage pulse. B, Plot of steady-state currents versus clamped membrane potential (V_m) of GmN70 oocytes bathed in 100 mm Na NO₃ (white squares) or 100 mm Na gluconate (black squares). Error bars show SEM of currents recorded from three separate oocytes. C, Current voltage relationship of nitrate-induced currents corrected for background currents (in the presence of gluconate) for GmN70-injected oocytes (white squares) or uninjected control ooctyes (black triangles).