Figure 6.
Transjunctional asymmetry of [Mg2+]i causes asymmetric Vj gating of homotypic Cx36-EGFP GJs. A, D, Transjunctional asymmetry in [Mg2+]i (see diagrams at the top of B and E for free Mg2+ concentration in pipette solutions and stimulation site) caused asymmetry in Vj-gating with decrease in gj for relative negativity on the low [Mg2+] side. Vj steps (±80 mV) of opposite polarities produced opposite effect on gj. Small-amplitude repeated Vj ramps (±20 mV, same as in Fig. 1A) were used to measured gj between Vj steps. B, E, gj–Vj relations (normalized to gj value at Vj = 0) measured by applying long (60 s) Vj ramps from 0 to +100 and −100 mV. Relative positivity on the high [Mg2+] side decreased gj. C, F, Asymmetric concentration of MgATP (C, top diagram) or K2ATP (F, top diagram) was associated with asymmetry of gj–Vj dependence (normalized to gj value at Vj = 0).