FIGURE 12.

Effects of nifedipine on K⁺-induced contraction and Pyk2 autophosphorylation. A and B, peak (A) and sustained (B) contractile responses to K⁺ were recorded in the absence and presence of the indicated concentrations of nifedipine after a 30-min pre-incubation with nifedipine or vehicle (Hepes-Tyrode's buffer). Peak force was recorded 1 min after the addition of K⁺ and sustained force at 10 min, and values are expressed as a percentage of the peak (A) or sustained (B) force in tissues treated with K⁺ in the absence of Ca²⁺ channel blocker (n = 4–5). Tissues were quick-frozen after a 10-min treatment with K⁺ for analysis of Pyk2 autophosphorylation by Western blotting. C, representative Western blots showing Pyk2 phosphorylation at Tyr-402 (pY402-Pyk2), total Pyk2, and actin as loading control. D, cumulative quantitative data with Pyk2 autophosphorylation expressed as -fold change relative to untreated tissue. Values represent the mean ± S.E. (n = 5). *, p < 0.001, **, p < 0.05, ***, p < 0.01, significantly different from the value of the K⁺-treated control in the absence of nifedipine.