FIGURE 3.

Inactive phorbol ester, 4α-phorbol, does not inhibit pinacidil-evoked currents through Kir6.2/SUR2B channels. A, whole cell recording from HEK293 cell stably transfected with Kir6.2/SUR2B. Currents were evoked using a series of 1-s voltage ramps from −100 mV to +100 mV from a holding potential of 0 mV every 15 s in 300 nm free intracellular Ca²⁺. K_ATP current was activated by superfusing the patch with 10 μm pinacidil (Pin), 1 μm 4α-phorbol (4αP), and 10 μm glibenclamide (Glib) were superfused in the presence of pinacidil as indicated by the solid bars. B, mean I-V relationship. Currents were elicited by a series of voltage steps from −100 to +100 mV in 20-mV increments. C, normalized mean currents at −50 mV in the presence and absence (Control) of 1 μm 4α-phorbol (mean ± S.E. (error bars), n = 4, ***, p < 0.001 compared with pinacidil).