Figure 2
Acetylcholine (ACh)-induced Ca2+ sensitization of murine bronchial smooth muscle. (A) A typical recording of contraction induced by Ca2+ (pCa 6.0 and 5.0) and ACh (10-5–10-3 M) with guanosine triphosphate (GTP; 10-4 M) in α-toxin-permeabilized bronchial smooth muscle isolated from a sensitized control mouse. In the presence of GTP, ACh induced further contractions even in the constant Ca2+ concentration at pCa 6.0, i.e., ACh-induced Ca2+ sensitization, in an ACh-concentration-dependent manner. (B) Concentration-response curves for ACh (10-5–10-3 M)-induced Ca2+ sensitization in α-toxin-permeabilized bronchial smooth muscle isolated from sensitized control (Control; open circles) and repeatedly ovalbumin-challenged (OA-challenged; closed circles) mice. The data are expressed as percentage increase in tension induced by ACh (10-5–10-3 M) in the presence of Ca2+ (pCa 6.0) and GTP (10-4 M) from the sustained contraction induced by pCa 6.0. Each point represents the mean ± S.E. from 6 experiments. The ACh-induced Ca2+ sensitization of bronchial smooth muscle contraction was significantly augmented in the OA-challenged mice (*P < 0.05 vs. Control group by unpaired Student's t-test).