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Aortic stiffness, as measured by carotid-femoral pulse wave velocity (PWV), is a powerful, independent predictor of vascular risk. PWV in muscular arteries is influenced by basal nitric oxide (NO) release. It is not known whether NO also influences carotid-femoral PWV. We examined the effects of an NO synthase inhibitor, NG-monomethyl-l-arginine (L-NMMA), on carotid-femoral PWV and aortic augmentation index (AIx, an indirect measure of arterial stiffness). To control for effects of L-NMMA on distending pressure, we used doses of norepinephrine and dobutamine that caused similar changes in mean arterial blood pressure (MAP). Healthy men (32 to 48 years old, n=8) were studied on 4 occasions and received, in random order, vehicle, L-NMMA (3 mg x kg(-1) by intravenous bolus followed by 3 mg x kg(-1) x h(-1)), norepinephrine (50 ng x kg(-1) x min(-1)), and dobutamine (2.5 to 10 microg x kg(-1) x min(-1)), each for 30 minutes. PWV and AIx were measured by carotid-femoral PWV and radial tonometry, respectively. L-NMMA and norepinephrine increased MAP by 7.8+/-1.7 and 9.7+/-2.1 mm Hg, respectively (each P0.99, P<0.0001). L-NMMA and norepinephrine increased AIx, but dobutamine decreased AIx (P<0.01 vs norepinephrine and L-NMMA). Effects of inhibition of basal NO release on carotid-femoral PWV can be explained by the change in MAP that this causes rather than any specific effect of NO inhibition within the aorta.
Stewart et al. (Tue,) studied this question.