Repetitive myocardial stunning in pigs is associated with an increased formation of reactive nitrogen species.

The “oxyradical hypothesis” of myocardial stunning proposes that superoxide, released on reperfusion, leads to contractile dysfunction via the production of the more reactive hydroxyl free radical from the iron catalysed Haber-Weiss reaction. However, superoxide reacts many times faster with nitric oxide (NO), than with ferric iron, leading to the formation of peroxynitrite (ONOO), which is a potent oxidising and nitrating agent with properties and reactivity similar to hydroxyl radicals. Consequently ONOO is a candidate for the initiation of oxidation reactions following brief ischaemia–reperfusion injury. The production of reactive nitrogen intermediates such as ONOO is reflected in vivo by the formation of the amino acid derivative 3-nitrotyrosine. Recently, we have developed a sensitive method for the quantitative analysis of tissue nitrotyrosine which avoids the artefactual formation of nitrotyrosine that can occur with more conventional protein preparative steps. The present study sought to test the hypothesis that myocardial stunning causes increased formation of tissue nitrotyrosine.