P1.5 age and hypertension strongly reduce aortic visco-elastic properties in rats at basal and matched blood pressure levels

Age and hypertension are major causes of large artery stiffening, a cardiovascular risk factor for heart and kidney damage. Long term hypertension induces vascular remodeling, accelerating vascular aging. The aged Spontaneously Hypertensive Rat (SHR) model is recognized for human cardiovascular pathology but discrepancies are apparent in studies of arterial stiffness. We performed experiments using a robust aortic visco-elasticity analysis via echotracking in 20 (n=6) and 80 week old SHR (n=8), and respective control Wistar Kyoto rats (WKY, n=6-6) at basal and matched levels of blood pressure (BP). After anesthesia (pentobarbital), abdominal aortic diameter and pressure were recorded and BP was decreased by clonidine i.v. At basal BP, aortic pulse distension, compliance, distensibility (AD) and wall viscosity (AWV) were reduced and stiffness index increased with age and hypertension and further altered with age + hypertension. BP being adjusted to 130 and 100 mmHg between groups, there was no difference between 20w old SHR and WKY but importantly the age effect was maintained in both WKY and SHR and accentuated by hypertension in old rats. At 130 mmHg, AD = 24.2±1 in 20w WKY, 20.3±1.8 in 20w SHR, 12.4±1.3 in 80w WKY and 6.1±0.7 in 80w SHR; AWV = 58±5, 58±9, 29±1 and 10±2 in the same groups. In conclusion reduced distensibility i.e. stiffening due to age is clearly shown here in both WKY and SHR as well as the effect of hypertension in aged rats. It will allow new investigations of the mechanisms and possible effect of drugs on aortic stiffness.