Hypertension is known to decrease arterial distensibility and systemic compliance. However, the arterial tree is not homogeneous, and it has been shown that the mediumsize radial artery does not behave like the proximal, elastic, large, common carotid artery. Indeed, radial artery compliance in hypertensive patients (HTs) has been shown to be paradoxically increased when compared with that in normotensive control subjects (NTs) at the same blood pressure level. To determine whether this increase was due to hypertension-related hypertrophy of the arterial wall, radial artery functional and geometric parameters from 22 NTs (mean±SD, 44±11 years) were compared with those from 25 age-and sex-matched never-treated essential HTs (48 ±12 years) by using a high-precision ultrasonic, echo-tracking system coupled to a photoplethysmograph (Finapres system),

This study determined the effects of long-term chemical sympathectomy with guanethidine (GN) on the mechanical properties and composition of the distal abdominal aorta in Wistar rats. GN was daily administered for 3 mo (3M-GN, from 1 to 12 wk), 5 wk (5W-GN, from 7 to 12 wk), and 8 days (8D-GN, from 11 to 12 wk). All experiments were performed at 12 wk of age to avoid age differences at examination. We used a high-resolution echo-tracking system to determine in situ, in the systolic-diastolic range, the aortic diameter-, compliance-, and distensibility-pressure curves in anesthetized rats. We observed an equivalent significant fall in the tyramine pressor response in all conscious GN-treated rats. Blood pressure was not affected by sympathectomy after 8 days and 5 wk of treatment but was significantly reduced in 3M-GN rats. Chronic sympathetic denervation increased aortic diameter and compliance in 8D-GN rats, compared with those obtained at the same distending pressure in control rats, suggesting vascular smooth muscle relaxation. In contrast, in 5W-GN and 3M-GN rats, the distensibility pressure-curves were significantly shifted toward lower levels of distensibility and pressure, indicating a decreased aortic distensibility at the same level of arterial pressure. Sympathectomy produced a significant reduction in the content of elastin, one of the most distensible components of the arterial wall in 5W-GN and 3M-GN rats. These results suggest that intact sympathetic nerves are necessary to maintain normal functional and structural properties of large arteries in rat. The reduction in aortic distensibility, in long-term sympathectomized rats, could have resulted from complex interactions between local aortic denervation, change in the set point of distending pressure, and changes in aortic smooth muscle tone and/or wall composition.

In this study we investigated whether there exists a periodic contractile activity of the radial artery, and we evaluated the impact of such an oscillatory behavior on the mechanical properties of this medium-sized muscular vessel. The internal diameter of the right radial artery was measured noninvasively in six healthy male volunteers aged 18-42 yr using a high-precision ultrasonic echo-tracking device. Blood pressure was simultaneously recorded on the same side at the middle finger by photoplethysmography. The electrical activity of the heart was monitored during the entire experiment by electrocardiography. The frequency components of the arterial diameter, blood pressure, and heart rate were obtained using spectral analysis. Under resting conditions, the radial arterial diameter exhibited a spontaneous oscillation with a period ranging from 45 to 70 s and an amplitude of 80 +/- 14 microns (+/- SE). No very low-frequency mode (< or = 0.02 Hz) was identified in either heart rate or blood pressure. These diameter oscillations affected the distensibility-pressure curves acquired simultaneously. Thus the 3-4% oscillatory variation in arterial diameter was paralleled by a 1.5- to 2-fold change in distensibility. These low-frequency oscillations of large arteries seem to be mediated by an intrinsic vascular mechanism.

Professeur à l' université Pierre-et-Marie-Curie. Centre de génétique moléculaire, Cnrs, ave nue de la Terrasse, 91 198 Gi fsur-Yvette Cedex, Fra nce. '

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