Enalapril acts through release of nitric oxide in patients with essential hypertension

Background: Endothelial dysfunction has been proposed as an etiological age nt in the pathogenesis of essential hypertension. Amongst the various antih ypertensive drugs, angiotensin converting enzyme inhibitors (ACEI) have bee n implicated in modifying the vascular endothelium. by the release of media tors that include bradykinin, nitric oxide, prostaglandins and thromboxane A2. Materials and Methods: To study the mechanism of action of enalapril, a n ACEI, serum reactive nitrite intermediates (RNI) and citrulline, by produ cts of nitric oxide metabolism were measured before and after treatment wit h enalapril in 25 consecutive patients of essential hypertension. Results: Following treatment serum RNI intermediate increased from a pretreatment va lue of 164.5 +/- 20.2 nmol/mL to a post treatment value of 266.9 +/- 47.3 n mol/mL (p < 0.05), however there was no significant change in the levels of citrulline (p > 0.1). There was no significant correlation between the sev erity of hypertension and serum RNI. Serum RNI levels were lower in the pos tmenopausal women but did not reach statistical significance. Conclusions: It is postulated that enalapril exhibits its antihypertensive property thro ugh release of nitric oxide.