Role of endothelial cell dysfunction in essential hypertension.

BACKGROUND: Hypertension is associated with functional and morphological alterations of the endothelium, which disturbs delicate balance of endothelium-derived factors resulting in endothelial dysfunction. The endothelial dysfunction could then facilitate the maintenance of elevated peripheral resistance, which would favor the occurrence of atherosclerosis. AIMS AND OBJECTIVES: The aim of the present study was to determine the circulating levels of vasodilators [nitric oxide (NO) and prostacyclin (PGI2)] and vasoconstrictors [endothelin I (ET-I) and thromboxane (TX)A2)], which reflect endothelial cell dysfunction. METHOD: Nitric oxide as nitrites and nitrates (NOx) were measured spectrophotometrically; ET-I, TXA2 (as TXB2) and PGI2 (as 6 keto PGFIalpha) were measured using enzyme immunoassay methods in 54 male subjects having predominantly untreated, mild hypertension and compared with age-matched 75 healthy controls. RESULTS: Significantly higher levels of ET-I (p<0.001) and TXB2 (p<0.001) were found in essential hypertension subjects (EHT) as compared to controls. No significant difference was observed in NOx and 6 keto PGFIalpha between the two groups. There was significant increase (p = 0.005) in the ratio of TXB2/6 keto PGFIalpha in EHT subjects as compared to controls. CONCLUSIONS: Elevated levels of vasoconstrictors in untreated essential hypertension subjects as compared to controls confirmed the presence of endothelial dysfunction, even in mild cases of hypertension. Early detection of endothelial dysfunction may be a useful measure to guide therapy before the damaging effects of hypertension manifests.