Figure 4.
Intracellular K2ATP and MgATP have opposite effects on gj and Vj-gating in HeLa cells expressing Cx36-EGFP GJ channels. A, C, Ij's recorded during repeated 35-s-long Vj ramps from 0 to −100 mV. Brief voltage steps of −10 mV were used to measure gj in between Vj ramps. Pipette solutions contained 10 mm K2ATP (A) or MgATP (C). B, D, First (purple) and last (cyan) gj–Vj relations (normalized to initial gj value at Vj = 0) measurements obtained from experiments shown in A and C, respectively. E, F, First (purple) and last (cyan) gj–Vj relations (normalized to initial gj at Vj = 0) obtained using the same Vj protocol as in A. Pipette solutions contained 1.5 mm EDTA (E) or 5 mm MgCl2 (F). In all gj–Vj plots, we assumed that the gj–Vj relation for Vj > 0 was the mirror image of that for Vj < 0 (i.e., symmetrical around Vj = 0) and the last gj–Vj plots normalized to gj at Vj = 0 (gray) are also shown for comparison. G, Changes in normalized gj for the different compositions of the pipette solutions shown at the bottom. Values were obtained from the ratios of the steady-state final gj to the initial gj. Numbers of independent experiments are shown in the histogram bars; *p < 0.05; ***p < 0.001; ns, nonsignificant p values.