Nitric oxide production and arachidonic acid metabolism in platelet membranes of coronary heart disease patients with and without diabetes

Aim: To evaluate the levels of nitrite (NO₂^-) and nitrate (NO₃^-) ions and the incorporation of [³H]arachidonic acid (AA) into phospholipids of platelet membranes from coronary artery disease (CAD) patients with and without diabetes (NIDDM). Subjects and Methods: Eighteen CAD patients (group A), 18 CAD patients with NIDDM (group B), and 20 healthy controls (group C) without dyslipidemia, peripheral vascular disease and hypertension were included in the study. The groups were matched for age, sex and body mass index. The diagnosis of CAD was confirmed by coronary angiography. The nitric oxide end products (NOx), NO₂^- plus NO₃^- ions in platelet membranes, were determined using a spectrophotometric method based on the Griess reaction. The turnover of phospholipids was evaluated by incorporation of [³H]AA into platelet membrane phospholipids. Results: A significantly smaller amount of NOx ions was in the platelet membrane of groups A (40 ± 8 μmol/l) and B (29 ± 10 μmol/l) than C (57 ± 6 μmol/l), p < 0.001. Conversely a significantly greater amount of [³H]AA was incorporated into platelet phospholipids of group B patients (5,123 ± 1,637 dpm/mg) than groups A (3,159 ± 1,253 dpm/mg; p < 0.002) and C (1,621 ± 417 dpm/mg). An inverse correlation between [³H]AA incorporation and NOx levels was established: r = -0.76 (p < 0.05, n = 36) in CAD patients. Conclusions: Diabetes in CAD patients decreased the ability to produce platelet-derived NO and affects AA metabolism. This may result in higher platelet sensitivity to aggregating stimuli.