RELATIONSHIPS OF SERUM URIC ACID WITH PLASMA RENIN ACTIVITY AND PLASMA ALDOSTERONE IN UNTREATED HYPERTENSIVE SUBJECTS

In experimental studies conducted in rats, raising serum uric acid (SUA) levels resulted in stimulation of intrarenal renin expression. Studies in humans exploring the association of SUA with plasma renin activity (PRA) yielded conflicting results. Moreover, little is known about the relationship between plasma aldosterone concentration (PAC) and SUA. The aim of our study was to analyse the relationships between SUA, PRA and PAC and the influence of age and gender on these relationships in a group of subjects with primary hypertension. We enrolled 281 patients (men 59%), with untreated primary hypertension and normal renal function. The study population wad divided in two subgroups on the basis of the median value of age (47 years). Spearman’s rank-correlation analyses showed that SUA was significantly associated with PRA and with PAC in the overall study population (rho = 0.16, p = 0.007; and rho = 0.23, p < 0.001, respectively), and in the subgroup of subjectsyounger than 47 years (rho = 0.19, p = 0.02; and rho = 0.33, p < 0.001, respectively). The separate analysis by gender disclosed a statistically significant correlation between SUA and PAC in men (rho = 0.20, p = 0.01), whereas in the same gender the correlation between SUA and PRA did not reach statistical significance (rho = 0.14, p = 0.08). No significant correlations were observed between the same variables in subjects older than 47 years and in women. All the associations between SUA, PRA and PAC lost statistical significance in logistic multiple regression analyses aimed at assessing the factors independently associated with an elevation of PRA and of PAC (third tertiles of their distribution). Our results, showing significant relationships of SUA with PRA and PAC only in univariate analyses, seem to suggest that the associations previously reported in some studies between these variables, and particularly that between SUA and PRA, may be mediated by various confounding factors, such as serum creatinine and body mass index