FIGURE 6.

Measurement of NADPH availability from the ratio Fex-340/Fex-380 of the fluorescence intensities excited by 340- and 380-nm light. Fluorescence emission was collected >420 nm. A, dependence of the Fex-340/Fex-380 fluorescence intensity ratio on time after bleaching in the presence of 5 mm glucose (●, n = 8 cells), 0.2 mm glutamine (▵, n = 7 cells), and without any substrate (○, n = 9 cells). The value of the ratio at 60 min after bleaching was used as a measure of NADPH availability. The arrows point to the values of the ratio for RAL and ROL (Fig. 2B). B, glucose (●) and glutamine (▵) support NADPH generation in a concentration-dependent manner; n ≥ 6 cells used at each substrate concentration. C, pyruvate (■) and lactate (▿) support NADPH generation; n ≥ 6 cells used at each substrate concentration. The error bars represent standard errors. Experiments were performed at 37 °C.