In the present study we hypothesized that age-associated changes in the renal aldosterone/mineralocorticoid receptor (MR) system may differ between normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). In WKY, body mass index significantly increased with age. Fat mass may operate as a confounding factor; therefore, WKY (WKY-FR) was pair-fed with SHR. Pair-feeding resulted in a 14% body weight reduction at the age of 52 weeks in WKY-FR. Renal oxidative stress was increased in aged WKY and SHR. Aged WKY and SHR had increased MR functionality, which correlated positively with increased plasma aldosterone levels, nuclear MR content and abundance of aldosterone effectors in the renal medulla. In contrast, decreases in nuclear MR content were observed in the renal cortex of both strains with aging. When compared to aged SHR, aged WKY-FR had decreased plasma aldosterone levels and decreased activation of the aldosterone/MR system in the renal medulla. Increases in renal oxidative stress and plasma aldosterone in aged WKY, to levels observed in SHR, were not sufficient to result in sustained increases in blood pressure. In conclusion, activation of the aldosterone/MR system is intensified by aging in SHR, whereas increases in body fat mass in WKY associate with hyperaldosteronism and oxidative stress.
Copyright © 2012. Published by Elsevier Inc.