FIGURE 6.
The highly specific endogenous PP1 inhibitor NIPP-1 obliterates the recovery of ICl(Ca) in the absence of internal ATP. A graph illustrates the mean time course of changes of normalized late ICl(Ca) recorded at +90 mV (1-s steps at 20-s intervals) in cells dialyzed with 3 mm ATP (filled squares; n = 4) or in the absence of ATP with (empty circles; n = 5) or without 100 pm NIPP-1 (empty squares; n = 9), as indicated. NIPP-1 enhanced ICl(Ca) rundown and abolished its delayed recovery seen in the absence of ATP (***, p < 0.001 relative to 0 ATP and no blockers). The extent of inhibition of ICl(Ca) by NIPP-1 was similar to the level of rundown induced by 3 mm ATP. n.s., not significant.