Figure 8. Wortmannin prevents tyrphostin B42 activation of K_ATP channels.

A, current clamp record of a cell dialysed with 5 mM ATP. Application of wortmannin (10 nM) for the time indicated had no effect on the resting membrane potential. Addition of tyrphostin B42 (10 μM) after exposure to wortmannin failed to hyperpolarize CRI-G1 cells. B, plot of the current-voltage relationships for voltage clamped currents obtained at the points specified in A: ○, control; •, wortmannin; □, tyrphostin B42 and wortmannin. Wortmannin prevented the tyrphostin-induced increase in K⁺ conductance.