FIGURE 4.

Effect of arginine and reactive nitrogen species on metformin action. A, effect of different concentrations of arginine on glucose uptake in L6 myotubes. L6 cells were incubated with 5 mm glucose with or without different concentrations of arginine for 2 h. B, effect of arginase inhibitors on metformin-induced glucose uptake in L6 myotubes. L6 cells were incubated with 5 mm glucose with or without 10 mm metformin, and combined with 10 μm NOHA or 1 μm BEC for 2 h, and then glucose uptake was measured. Met, metformin; NOHA, Nω-hydroxy-nor-l-arginine; BEC, (S)-(2-boronoethyl)-l-cysteine, HCl. *, p < 0.05 versus control. C, effect of SIN-1 on glucose uptake in L6 myotubes. L6 cells were incubated with 5 mm glucose with or without 1 mm SIN-1 for 2 h, and then glucose uptake was measured as described under “Experimental Procedures.” *, p < 0.05 versus control. D, effect of SIN-1 on palmitate oxidation in L6 myotubes. L6 cells were incubated with 120 μm palmitic acid with or without 1 mm SIN-1 for 3 h, and then palmitate oxidation was measured as described under “Experimental Procedures.” *, p < 0.05 versus control. Data are expressed as per mg of cellular protein.