A novel procedure for generating both nitric oxide and superoxide in situ from chemical sources at any chosen mole ratio. First application: Tyrosineoxidation and a comparison with preformed peroxynitrite

The first method for generating . NO and O-2(.-) at any known, constant rat io has been developed. Spermine NONOate and di(4-carboxybenzyl)hyponitrite decay with first-order kinetics and exactly equal rate constants (half-live s of 80 min) at 37 degreesC and pH 7.5 to give 200 and 40 mol % . NO and O- 2(.-), respectively. Tyrosine oxidation to dityrosine and 3-nitrotyrosine ( the major and minor products under the conditions used in these experiments ) has been studied (mainly in the presence of CO2) using various different ratios of the rates of formation of . NO and O-2(.-). The . NO/O-2(.-) = 1. 0 product profiles are very similar to those of the products derived from e qual amounts of . NO and O-2(.-) generated at a . NO/O-2(.-) ratio of 1.0 f rom SIN-1 but are very different from those derived from preformed peroxyni trite. All the experimental results can be explained in terms' of free radi cal chemistry. The product profiles at all the . NO/O(2)(.-)ratios could be satisfactorily simulated provided an important group of reactions which le ad to the consumption of dityrosine was included.