Effects of high salt diet on age‐related hypertension and central AngII‐induced cardiovascular responses

Abstract

Angiotensin II (AngII) plays an important role in both age‐related and salt‐induced hypertension. The aim of this study was to investigate the effects of age and high‐salt (HS) diet on resting blood pressure (BP) and heart rate (HR), as well as on central AngII‐induced cardiovascular responses. Young (5 mo) and old (27 mo) male F344xBN rats were fed regular chow or HS (8%) for 11 days. BP and HR were measured using radiotelemetry. AngII (10ng/μl/h) or CSF was infused intracerebroventricularly before and during HS for 3 days with osmotic pumps. Old rats had significantly higher BP (108.3±3.6 mmHg) than young (96.1±3.1 mmHg, p<0.05). HS diet caused significant increases in BP in both young and old groups (young: 99.0±3.5, p<0.01; old: 116.3±4.1, p<0.001), but the increase in BP was significantly higher in old rats (p<0.05). In contrast, HR didn't change significantly in either group in response to HS diet. AngII‐induced BP increases were significantly diminished in old rats (4.4±2.0 %) compared with young (12.6±1.3%, p<0.05), while HR responses were similar (15.8±4.0% and 13.5±2.1%). HS diet enhanced AngII‐induced BP and HR elevations in both age groups, but BP increases in old rats (5.9±1.7%) were still significantly lower compared with young (18.8±8.1%, p<0.05). Our findings indicate that sensitivity of BP to HS diet increases with age, and that central AngII‐induced pressor responses are diminished in old rats compared with young both under control conditions and during HS diet treatment.Supported by the Medical Research Service of the Department of Veterans Affairs, by an award from the American Heart Association and by a TUBITAK scholarship.