RESUMO
Objectives: This study aimed to evaluate a new simple colorimetric method for the assay of endothelial nitric oxide synthase activity in clinical researches and to compare between the role of vanadium chloride and nitrate reductase enzyme in the assay method. Methods and materials: The new method involved using RBCs lysate to measure eNOS of the endothelium, using NADPH recycling system to enable the colorimetric measurement of eNOS, and using vanadium chloride to converting nitrate to nitrite. The method repeated again using nitrate reductase then vanadium results were compared with nitrate reductase results. The clinical study involved sixty patients who were randomly divided into two groups; group one received atorvastatin 40 mg daily, group two (control group) received placebo capsules. Patients were examined both before and after six weeks for endothelial nitric oxide synthase (eNOS) and for international index of erectile function-5 (IIEF-5) scores. Results: In comparison to nitrate reductase, vanadium showed no significant difference in eNOS activity indicating similar role and activity. However, In comparison to control group, atorvastatin showed a significant increase in eNOS (48.16% for vanadium, and 44.3% for nitrate reductase, P<0.05). Also, atorvastatin showed a significant increase in IIEF-5 score (39.16%, P<0.05) and there was a significant correlation between eNOS and IIEF-5 score (P<0.05). Conclusion: The study recommended this method for assaying eNOS using RBCs lysate, NADPH recycling system and vanadium chloride. This method is simple, reliable, and suitable for routine use in clinical researches.