PLASMA NITRITE NITRATE LEVEL IS INVERSELY CORRELATED WITH PLASMA LOW-DENSITY-LIPOPROTEIN CHOLESTEROL LEVEL/

Background: Plasma nitrite/nitrate (NOx) is a stable end product of th e vasodilator nitric oxide (NO). However, there are few reports about plasma NOx levels in humans. Hypothesis: The purpose of this study was to assess the availability of plasma NOx for evaluating basal endogen ously-synthesized or endothelium-derived NO, and to examine whether NO x levels are lowered in patients with coronary artery disease (CAD) or its risk factors. Methods: Plasma NOx levels were measured using an a utomated system based on the Griess reaction. NOx levels for a 24-h pe riod reproducibly became lowest at 6 A.M. in restricted healthy volunt eers, and became stable in inpatient volunteers at 6 A.M. within 4 day s after admission. Results: Based on these findings, NOx levels at 6 A .M. in inpatients can be considered as the basal levels. In 40 inpatie nts suspected of CAD (28 men, 12 women; mean age 60 +/- 11 years). the basal levels of NOx were not related to CAD and its risk factors, exc ept for hypercholesterolemia. The NOx level of patients with hyperchol esterolemia was significantly lower than that of patients with normal cholesterol (n = 16.34 +/- 16 mu mol/l vs. n = 24, 49 +/- 23 mu mol/l, p < 0.03). Furthermore, the NOx levels correlated negatively with the total cholesterol and low-density lipoprotein cholesterol levels (r = -0.40, p < 0.01; r = -0.47, p < 0.003. respectively), but not with ot her lipid fraction levels. Conclusion: The results suggest that the qu antity of basal endothelium-derived NO synthesis may be decreased in t he presence of hypercholesterolemia.