The role of central oxidative stress in age‐related, salt‐sensitive sympathoexcitation

We have previously shown that sensitivity of blood pressure to a high salt (HS)-diet increases with age. The aim of the study was to elucidate whether central oxidative stress mediates peripheral sympathoexcitation which is associated with elevated blood pressure. Young (5 mo, n=8) and old (27 mo, n=8) male F344xBN rats were fed with standard rat chow or 8% HS diet for 11 days. mRNA levels of adrenomedullary tyrosine hydroxylase (TH) and dopamine-β hydroxylase (DβH) which are indicators of sympathoexcitation, increased significantly with age, with a further increment in TH due to the HS diet. While hypothalamic levels decreased with age, HS diet caused a significant increase in TH levels in the old rats. Furthermore, hypothalamic p22phox mRNA and gp91phox protein, subunits of NAD(P)H oxidase, as well as NAD(P)H oxidase activity increased in response to HS diet in the old rats, while antioxidant enzymes (CuZnSOD, MnSOD, and catalase) decreased with age yet remained unaltered with the HS diet. These results suggest that central oxidative stress especially NAD(P)H oxidase dependent superoxide might be responsible for age-related salt sensitive sympathoexcitation. Supported by the Medical Research Service of the Department of Veterans Affairs, American Heart Association, National Institute of Aging and by a TUBITAK scholarship.