Figure 6. Effects of CysLT₁ receptor antagonists on Epac activation and PKA activity.

(A) The monochrome CFP and FRET images showing the cytosolic distribution of the fluorescent Epac probe in 16HBE14o- cells transfected with CFP-Epac-YFP. (B) Representative pseudocolor images of CFP/FRET emission ratios before and after the addition of 8-CPT-2′-O-Me-cAMP. (D) Real-time cAMP changes (normalized CFP/FRET emission ratio) recorded in cells stimulated with 50 µM 8-CPT-2′-O-Me-cAMP with or without 1 µM pranlukast shown in (B). The agents were added at time zero. (C) Summarized data showing the effect of CysLT₁ receptor antagonists on the CFP/FRET emission ratio. Each column represents the mean ± S.E. (n = 8–10). (*, p<0.05, Student's t-test compared with control). (E) Confluent 16HBE14o- cells were treated with either vehicle alone (control), 100 µM UDP, or UDP with different CysLT₁ receptor antagonists (1 µM) for 5 min. PKA activity was measured as a function of fluorescence intensity. (F) Summarized data showing the relative fluorescence level as compared with the control level. Each column represents the mean ± S.E. (*, p<0.05, n = 4, one-way ANOVA with Bonferroni post-hoc test).