REACTION BETWEEN IMIDAZOLINEOXIL N-OXIDE (CARBOXY-PTIO) AND NITRIC-OXIDE RELEASED FROM CULTURED ENDOTHELIAL-CELLS - QUANTITATIVE MEASUREMENT OF NITRIC-OXIDE BY ESR SPECTROMETRY

The performance of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide for the monitoring agent of nitric oxide was investigated. The agent (125-500 mu M) was mixed with equal volume of nitric oxide solution, and aliquots of the mixture were applied to ESR spectroscopy. ESR spectra of 2-(4-carboxyphenyl)-4,4,5,5-tetramethyimidazoline-1-oxyl, a product of the agent reacted with nitric oxide, were observed. A linear relationship was observed between the amplitude of the signal and concentrations of nitric oxide up to 80 mu M. Endothelial cells cultured on microcarriers were packed in a column, perfused with Krebs solutions and the effluent was mixed to the agent. The same ESR spectra were obtained and amplitude of the signal was increased by bradykinin (3-300nM), decreased by preincubation of N-G-monomethyl-L-arginine (3-100 mu M) and reversed by following incubation of L-arginine (100 mu M).