Fig. 4.
Glutamine-evoked cAMPi responses in GLUTag cells. GLUTag cells were transfected with the cAMP probe, Epac2 camps. FRET was measured as the YFP/CFP ratio by exciting the cells at 435/10 nm (A inset shows example image) A, Representative trace showing the CFP/YFP fluorescence ratio (reflecting [cAMP]i) recorded from an individual cell after addition of 10 mm glutamine and the positive control 10 μm forskolin and 10 μm IBMX (F/I). B, Mean cAMP changes in response to a vehicle control (con) and a range of L amino acids (10 mm of each), as indicated (open bars). Gln (10 mmol/liter) was also tested in the absence of extracellular Na+ (Gln, gray bars). CFP/YFP ratios in the presence of the test agent were expressed relative to the positive control performed in each experiment, as shown in A. Data represent the mean and sem. **, P < 0.01; ***, P < 0.001 compared with vehicle by Student's t test.