Fig. 2.

NGF stimulates arginine metabolism in primed PC12 cells. (A) Induction of arginase I expression in primed PC12 cells after NGF treatment. Western blot of lysates from PC12 cells treated with NGF (50 ng/ml) for 14 h is shown. (B) Quantification of arginase I expression (control, 1.15 ± 0.02; NGF, 1.92 ± 0.08). Data are presented as mean ± SEM from three experiments. ∗, P < 0.01. (C) Arginase activity. Primed PC12 cells were treated with NGF (50 ng/ml) for 14 h followed by addition of arginine labeled with ¹⁴C at the guanido group and incubated for 1 h. Radiolabeled urea was separated by TLC and quantified by scintillation counting (control, 2,061 ± 112; NGF, 6,976 ± 226; NGF plus BEC, 257 ± 29 in dpm). Results are presented as mean ± SEM from three independent experiments. ∗, P < 0.01. (D) ODC. Primed PC12 cells were treated with NGF (50 ng/ml) for 14 h followed by addition of arginine labeled with ¹⁴C at the carboxyl group and incubated for 1 h. CO₂ was captured by 1 M KOH and measured by scintillation counting (control, 164 ± 7.5; NGF, 397 ± 33; NGF plus BEC, 110 ± 9.4; NGF ± DMFO, 94 ± 10 in dpm). Results are presented as mean ± SEM from three independent experiments. ∗, P < 0.01.