Lack of influence of dietary nitrate/nitrite on plasma nitrotyrosine levels measured using a competitive inhibition of binding ELISA assay

Abstract

The action of peroxynitrite in vivo has been proposed to account for the involvement of nitrotyrosine in the pathogenesis of many diseases. However, it has been demonstrated that nitrite under acidic conditions, similar to those in the human stomach, also has the ability to nitrate tyrosine. Dietary nitrate is also implicated in the progression of gastritis and gastric cancer and elevated levels of nitrate are found in many disease states in which nitrotyrosine may play a role. Thus, we investigated whether the dietary nitrate intake might contribute towards the plasma protein-bound levels of nitrotyrosine.Seven healthy, non-smokers participated in a two-day study consisting of a nitrate-low control day followed by a day during which three nitrate-rich meals were consumed. Maximal urinary excretion was attained 4–6 hours after consumption of a meal and the maximum was proportional to the dose. Plasma nitrate was elevated nine-fold, 1 hour after consumption of a meal containing 128.3 mg nitrate. Plasma nitrated protein levels did not appear to alter significantly from basal 1 hour after supplementation with a nitrate-rich meal. Thus dietary nitrate does not appear to contribute to the levels of plasma nitrated proteins, as determined using a competitive inhibition of binding ELISA assay, but this does not preclude any contribution it may make to the total body burden of nitrotyrosine.