Nitrite plasma levels in acute and chronic coronary heart disease.

Background: The authors carried out a study on the plasmatic levels of nitrites, which are the sole stable metabolites of nitric oxide (NO), in a group of subjects suffering from various clinical forms of coronary artery disease, aimed at evaluating the endothelial production of NO in acute and chronic ischemic conditions.
Methods: Our series consisted of 104 female subjects (mean age 65 +/- 5) subdivided into: a) 10 subjects with acute coronary heart disease (myocardial infarction); b) 32 with chronic non hypertensive coronary heart disease (CHD); c) 30 with hypertensive CHD (arterial blood pressure over 160/95 mmHg); d) 32 with CHD and hypercholesterolemia (values over 250 mg/dl). Thirty-seven female subjects (mean age 58 +/- 7) without internistic diseases were considered as control subjects. For each sample the plasmatic levels of nitrites were determined by the Gutman and Hollywood method.
Results: We discovered that in the patients with chronic coronary heart disease (CHD) the mean value of nitrites was 18 +/- 0.3 mumol/L, not significantly different from the controls (17 +/- 0.5 mumol/L). In the patients with acute CHD the nitrite plasma level were significantly (p < 0.05) higher (30 +/- 2.2 mumol/L) compared to the controls and the patients with chronic CHD. In the group of patients with hypertensive CHD the mean nitrite value was 20 +/- 0.6 mumol/L, significantly (p < 0.05) higher in comparison with the group of non-hypertensive CHD patients (14 +/- 0.3 mumol/L). In the subjects with CHD and hypercholesterolemia the mean value of nitrites was sharply elevated, (25 +/- 1.0 mumol/L), with a highly significant difference (p < 0.01) as compared to the normolipemic CHD patients.
Conclusions: These results lead to the hypothesis that: strong NO production may play a compensatory and protective role during acute myocardial hypoxia; NO defective synthesis may depend on an exhaustive endothelial adjustment in subjects with long-term CHD; a significant increase of the relaxing factor in hypertensive conditions exists; a highly enhanced synthesis of the plasmatic nitrites in hypercholesterolemic patients means an engagement of NO to neutralize the endothelium-damaging molecular substances and particularly the oxided LDL.