Fig. 4.

Effects of ouabain and isoproterenol on changes (Δ) of FRET from YFP-CBD1-CFP during spontaneous contractions of transgenic zebrafish hearts. A: time course of ΔFRET (YFP-to-CFP ratio) before and after application of 1 μM ouabain or isoproterenol. B: summary data comparing ΔFRET in the absence and presence of ouabain or isoproterenol. ΔFRET is calculated as the difference of the YFP-to-CFP ratio between contraction and relaxation. Data are normalized against control. Values for n are 5 (0.1 μM ouabain), 4 (1 μM ouabain), 4 (0.5 μM isoproterenol), and 4 (1 μM isoproterenol). *P < 0.05.