838 Activation of the aldosterone/MR system by aging in spontaneously hypertensive rats

Abstract

In the present study we hypothesised 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 (BMI) significantly increased with age. Fat mass accumulation may operate as a confounding factor therefore WKY were submitted to 15% food restriction (WKY-FR) from 5 to 13 and 52 weeks of age. Renal oxidative stress was increased in aged WKY and SHR. Long-term FR significantly reduced the BMI and decreased renal oxidative stress when compared to age-matched 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, when compared to aged WKY and 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 hyperaldosteronism in WKY is associated with increases in body fat mass.