Nitrite plasma levels in acute and chronic coronary heart disease

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.

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.

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.

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.