WGA labeling and voltage-clamp fluorometry of CHO cells expressing voltage-gated channels. (A) hHv-1 (top) and Shaker-IR (bottom) currents were recorded before (left) and after (right) WGA labeling (50 µg/ml). Middle panels are currents before (black) and after (red) WGA wash-in at 60 mV. Cells were held at −80 mV, hHv-1 depolarized for 0.5 s from −50 to 100 in 10-mV increments, and Shaker-IR depolarized for 0.2 s from −70 to 60 mV in 10-mV increments. (B) G-V curves of hHv-1 (V_0.5 = 68 ± 6 mV, n = 8, triangles) and Shaker-IR (V_0.5 = −18 ± 1 mV, n = 5, circles) before (closed) and after (open) WGA treatment. hHv-1: V_0.5 = 67 ± 8 mV, n = 9; Shaker-IR: V_0.5 = −11 ± 1 mV, n = 6. (C) Voltage-clamp fluorometry traces from cells labeled with WGA-pHRho (red) and homemade WGA-fluorescein (green). hHv-1 (left) was held at −80 mV, and changes in fluorescence were elicited from 4-s depolarizations from 0 to 100 mV in 20-mV increments. Shaker-IR R362H (right) was held at 30 mV, and fluorescence was elicited from 4-s command voltages from −120 to −20 mV in 20-mV increments. (D) Representative fluorescent images of CHO cells 10–210 min after labeling with WGA-pHRho for 30 min; scale bars represent 10 µm. (E) Bar graph of ΔF/F₀ from hHv-1 expressing cells after a 4-s 80-mV depolarization versus time after WGA-pHRho labeling. n = 3 experiments. Error bars represent SEM.