NG-Hydroxy-L-Arginine Releases from Endothelial Cells Nitric Oxide which Increases cGMP in RFL-6 Fibroblasts

The release of nitric oxide (NO) by NG-hydroxy-L-arginine (L-OHArg) from endothelial cells (ECs) grown in culture was assessed by two bioassays. The first was a cascade bioassay system, in which the effluent from a column of ECs grown on beads superfused a cascade of isolated endothelium-denuded rabbit aortic strips. Exclusion of calcium from the Krebs' buffer perfusing the ECs (but not from the cascade) diminished the relaxant effects of L-OHArg. Growing the ECs in the presence of dexamethasone did not affect the relaxations of the bioassay cascade induced by L-OHArg. However, these relaxations were potentiated by superoxide dismutase (SOD) and inhibited by haemoglobin, but not inhibited by NG-nitro-L-arginine methyl ester (NO2 ArgMeE). The second bioassay was a transfer assay, in which accumulation of cGMP was measured in detector, RFL-6 fibroblast cells. The accumulation of cGMP induced by the basal release of NO from ECs was increased by L-OHArg and by SOD. However, L-OHArg, unlike SOD, did not scaven...