Figure 2. Effects of kinase inhibitors on Ca²⁺ sensitization of force induced in permeabilized guinea-pig ileum by GTPγS.

A, guinea-pig ileum longitudinal smooth muscle permeabilized with β-escin was contracted by increasing [Ca²⁺] from pCa 9 to 4.5 and relaxed by returning to pCa 9. Transfer to pCa 6.5 solution failed to elicit a significant contraction but subsequent transfer to pCa 6.5 + GTPγS (100 μM) evoked Ca²⁺ sensitization of force. The effects of increasing concentrations of three kinase inhibitors (Y-27632, HA1077 and H-7) on Ca²⁺ sensitization were recorded. B, correlation between IC₅₀ values for inhibition of Ca²⁺ sensitization and the known K_i values for inhibition of ROK (n = 5).