Fig. 8. Comparison of the kinetics of FRET ratio and CBF changes during and after stimulation with cAMP or forskolin. Infected and differentiated human airway epithelial cells were either perfused apically with 1 µM, 10 µM or 20 µM forskolin (non-permeabilized cells; n=9) or basolaterally with 20 µM, 50 µM or 100 µM cAMP (permeabilized cells; n=7). The top of the graph shows an example of a permeabilized cell perfused basolaterally with 100 µM cAMP. The left side of the graph depicts the time to increase FRET-ratio (black) or CBF (gray) from baseline to their maxima in seconds, which were statistically indistinguishable (P>0.05). The right side depicts the times for the FRET ratio and CBF to return to baseline from their maxima. In each case, CBF decreased significantly slower than the FRET ratio (P<0.05 for all pairs).