Figure 1. Pak inactivation inhibits ACh‐stimulated tension development in tracheal smooth muscle tissues .

A, pak Thr423/Thr402 (T423/T402) phosphorylation was determined in tracheal smooth muscle tissues after 1, 2 or 5 min ACh stimulation or without stimulation (US). Immunoblots against phospho‐Pak T423/T402 and Pak1 were obtained using a site‐specific phospho‐Pak T423/T402 antibody and Pak1 antibody. The ratio of phospho‐Pak to Pak1 was determined for each sample (n = 11). B, Pak activation in response to 5 min ACh stimulation was inhibited in smooth muscle tissues by expressing Pak K299R (n = 9) or by treating the tissues with the Pak inhibitor, IPA3 (n = 6). C, contractile force in response to ACh is shown for tissues before and after they were transfected with plasmids encoding WT Pak, Pak1 K299R or no plasmids (Sham treated) (n = 12). Treatment with IPA3 also significantly inhibited ACh‐induced tension development compared to tissues not treated with IPA3 (No inhibitor) (n = 8). All force measurements were normalized to Sham response (91.3 ± 7.8 mN mm⁻²) or No inhibitor response (93.0 ± 9.0 mN mm⁻²). All values are means ± SEM. ^*Significant difference between treatment groups (P < 0.05).