DECREASED EXCRETION OF NITRATE AND NITRITE IN ESSENTIAL HYPERTENSIVESWITH RENAL VASOCONSTRICTION

Most hypertensive patients exhibit increased renal vascular resistance (RVR). This study was designed to investigate whether there exists an y relationship between RVR and the production of nitric oxide (NO) in patients with essential hypertension. The study was performed in 49 no n-treated patients with mild-to-moderate essential hypertension, and 2 0 age- and sex-matched normotensive subjects on a controlled sodium di et. Renal hemodynamics was measured in terms of the clearance of para- aminohippuric acid and inulin. Urinary excretion of nitrate and nitrit e (NO3- plus NO2-) was determined as an index of NO production. As com pared with normotensives, hypertensive patients exhibited higher (P < 0.001) RVR and lower (P < 0.05) urinary excretion of NO3- plus NO2-. W ith the 100% confidence (upper) limit of the normotensive population a s a cut-off point, a subgroup of 30 hypertensives had an abnormally hi gh RVR. The excretion of (NO3- plus NO2-) was lower (P < 0.005) in hyp ertensives with high RVR than in normotensives and the remaining hyper tensives. No differences were found in the urinary excretion of NO3- p lus NO2- between normotensives and hypertensives with normal RVR. Stat istically significant associations were seen between diastolic blood p ressure and RVR (r = 0.341, P < 0.05) and urinary excretion of NO3- pl us NO2- (r = -0.387, P < 0.01) in all hypertensives. These results ind icate that there is a subgroup (61%) of hypertensive patients with dim inished urine levels of NO3- plus NO2- in which RVR is abnormally incr eased. Thus, it is suggested that in essential hypertension a diminish ed renal ability to produce NO by the endothelium may be involved in e xaggerated renal vasoconstriction.