Significance of plasma nitric oxide/endothelial-1 ratio for prediction of coronary artery disease.

Vascular tone is regulated by vasodilators and vasoconstrictors. Endothelin-1 (ET-1) is the predominant vasoconstrictor peptide that constricts vascular smooth muscle, whereas nitric oxide (NO) is the primary vasodilator peptide that relaxes vascular smooth muscle. In this study, the authors examined whether NO/ET-1 ratio is a useful marker for detecting coronary artery disease (CAD), by comparison with evaluation based on vascular endothelial (VE) function. They measured plasma NOX and ET-1 by using ENO-200 and radioimmunoassay, in 38 subjects with normal (NL) coronary arteries (NL group; mean age, 60 +/-12 years) and 25 subjects with CAD (CAD group; mean age, 69 +/- 6 years). VE function (randomized endothelium-dependent [D] and endothelium-independent [I] VE function) was assessed by measuring brachial artery (BA) diameter by using high-resolution ultrasound (7.5 MHz). Soon after these procedures, symptom-limited exercise testing was performed. There were no statistically significant differences in serum lipid concentrations or VED function between the groups. However, the CAD group had a significantly lower NO/ET-1 ratio (1.2 +/- 1.1 vs 2.7 +/- 2.2, p < 0.01) and BA diameter after sublingual nitroglycerin (VEID function: 6 +/- 7% vs 10 +/- 4%, p < 0.05). As expected, the ST segment and treadmill exercise duration were significantly lower in the CAD group. Sensitivity and specificity for detecting CAD by plasma NO/ET-1 ratio (> or =2 .0) were 90% and 85%, respectively; sensitivity and specificity for detecting CAD by ST depression (> or =1 mm) were 80% and 78%, respectively. The present results suggest that plasma NO/ET-1 ratio is a useful biological marker for predicting CAD.