Vayssettes-Courchay C, Ragonnet C, Isabelle M, Verbeuren TJ. Aortic stiffness in vivo in hypertensive rat via echo-tracking: analysis of the pulsatile distension waveform. Am J Physiol Heart Circ Physiol 301: H382-H390, 2011. First published May 20, 2011 doi:10.1152/ajpheart.00094.2011.-Large-artery stiffening is a major risk factor in aging and hypertension. Elevated blood pressure (BP) and vascular wall properties participate in arterial stiffening; we aimed to evaluate their respective role by combining echo-tracking and the spontaneously hypertensive rats (SHR) treated with low doses of a nitric oxide synthase inhibitor, shown to have arterial stiffening. Normotensive [Wistar-Kyoto (WKY)], SHR, and SHR treated for 2 wk with N G -nitro-L-arginine methyl ester (SHRLN) were anesthetized; BP and distension (pulsatile displacement) of the aortic walls with the ArtLab echo-tracking device were measured. Stiffness index increased in SHRLN vs. SHR; compliance, distensibility, and the slopes and area of the distension-pressure loop curve decreased. The pulsatile distension and pressure waveforms were strongly altered in SHRLN. Maximal values were decreased and increased, respectively, and the waveform kinetics also differed. Thus the area under the curve adjusted to heart rate (AUC/ms) was calculated. Acute BP reductions were induced by diltiazem in SHR and SHRLN, to levels similar to those of WKY. In SHR, compliance, distensibility, stiffness index, and the ascending slope of the distension-pressure loop reached the values of WKY, whereas they were only partially improved in SHRLN. Aortic distension (maximal value and AUC/ms) and the area of the distension-pressure loop were improved in SHR, but not in SHRLN. These data confirm the aortic stiffening induced by nitric oxide reduction in SHR. They show that the ArtLab system analyzes aortic stiffness in rats, and that the aortic pulsatile distension waveform is a parameter strongly dependent on the vascular wall properties.hypertension; compliance; distensibility; pulse-wave velocity; nitric oxide; spontaneously hypertensive rats ARTERIAL STIFFENING IS A MAJOR cardiovascular risk factor (6,17,26,27) in hypertension, end-stage renal disease, hypercholesterolemia, obesity, and diabetes (9,12,21,28). It is also an age-dependent alteration of the vascular wall (21) that has been defined as an early vascular aging factor (22). Elevated blood pressure, inflammation, endothelial dysfunction, remodeling, and hypertrophy are closely related factors that lead to organ damage and vascular stiffening. In hypertension, the long-term elevation of blood pressure leads to endothelial damage and vascular wall remodeling. It has also been proposed that remodeling may precede the hypertensive state (30). In hypertensive patients, major therapeutic targets to avoid cardiovascular events are decreases in blood pressure and improvement of the vascular wall protection (6, 21). Up until now, it remains difficult in humans and in animals to separate the causal effects of blood pressure eleva...