Production of an EDRF-like activity in the cytosol of N1E-115 neuroblastoma cells

Accumulation of cyclic GMP in cultured rat lung fibroblasts was used to test the hypothesis that N1E-115 neuroblastoma cells produce an endothelium-derived relaxing factor (EDRF)-like activity. By using this assay, the production of an EDRF-like activity in homogenates and cytosolic fractions of N1E-115 neuroblastoma cells was observed. Detection of the activity required the presence of superoxide dismutase and was inhibited by hemoglobin. Production of the EDRF-like factor was dependent on L-arginine and NADPH. The apparent Km for L-arginine was 1.25 microM and the apparent Km for NADPH was 1.67 microM. The production of the EDRF-like activity was inhibited by the L-arginine analogs, NG-monomethyl-L-arginine and NG-nitro-L-arginine, with apparent Ki values of 1.0 and 0.3 microM, respectively.