Plasma nitrate as an index of nitric oxide formation in patients with acute infectious diseases.

In humans, the role of nitric oxide (NO) in host defence is controversial. We prospectively studied plasma levels of nitrate, the stable end-product of NO formation, during acute infection in 43 patients controlled with regard to dietary nitrate/nitrite. During acute gastroenteritis the mean plasma nitrate level was significantly increased compared with at recovery 4-5 weeks later (118 vs. 32.5 micromol/l; p < 0.001), in contrast with the findings in patients with acute pneumonia (PN; 34.6 vs. 42.8 micromol/l) or febrile urinary tract infection (UTI; 27.7 vs. 31.3 micromol/l). In a second group of 20 retrospectively studied patients with severe PN or UTI, of whom 70% were bacteraemic, no significantly increased nitrate levels could be demonstrated during the acute stage of infection. These findings indicate that increased NO production, as measured by plasma nitrate, is not a general finding in patients with acute infectious diseases, but may rather be associated with certain pathogens or sites of infection.