Figure 2. Inhibition of I_Ks by tyrphostin A25.

A, reversible inhibitory effect of 20 μm tyrphostin A25 (A25) on the amplitude of the I_Ks tail in a representative myocyte. B, records and I–V relationships obtained at the times indicated by the data breaks in A. C, dependence of I_Ks inhibition on the concentration of tyrphostin A25. Myocytes were treated with single concentrations of the inhibitor for ∼8 min, and the amplitude of the tail current at that time was expressed as a percentage of the control (predrug) amplitude. The Hill equation fitting the data has an IC₅₀ of 12.3 ± 2.1 μm and a coefficient of 1.0 ± 0.2. Number of myocytes is shown in parentheses.