The purpose of the present study was to determine the effects of chronic sinoaortic denervation on the mechanical properties and composition of the abdominal aorta in Wistar rats. We used a high-resolution echotracking system to determine in situ under physiological conditions of blood flow and arterial wall innervation the aortic diameter-, compliance-, and distensibility-pressure curves in 16-week-old anesthetized rats that had been denervated at 10 weeks of age for 6 weeks (n = 8). Compared with sham-operated rats (n = 8) we observed a marked reduction of baroreflex response and increase in overall mean blood pressure variability as measured by standard deviation and spectral analysis in sinoaortic-denervated rats. Mean blood pressure was not affected by sinoaortic denervation in both conscious and anesthetized rats. Sinoaortic denervation significantly shifted the distensibility-pressure curve toward lower levels of distensibility, indicating a decreased aortic distensibility for a given level of arterial pressure. Sinoaortic denervation produced a significant increase of aortic wall cross-sectional area and collagen content, one of the less-distensible components of the arterial wall. These results suggest that intact arterial baroreceptors are necessary for maintaining normal functional and structural properties of large arteries in rats. The reduction in arterial distensibility in chronic sinoaortic-denervated rats may have resulted from different factors, including the initial hypertensive phase, aortic wall hypertrophy, and increase in collagen content. The changes in aortic wall structure and related reduction in aortic distensibility, in addition to other mechanisms, might have been direct consequences of an increased blood pressure variability.

SUMMARYRed blood cells are capable of transport and accumulation of catecholamines. The aim of this paper is to characterize the catecholamine transport system in the human red blood cell and in particular that of dopamine. Dopamine, noradrenaline and adrenaline enter the red blood cell by a similar process, which shows saturation kinetics with , and cyanine suggest that catecholamine transport is not mediated by the Na+-H+ exchanger, the anion exchanger or a system similar to that responsible for dopamine uptake in either synaptosomes or the proximal tubule. However, choline inhibits the influx of dopamine with an 1C50 value of 17,uM and stimulates the efflux of dopamine with a Km value of 8 20 /LM. These results strongly suggest that dopamine is transported by the choline exchanger previously reported to be present in red blood cells. Probenecid inhibits dopamine uptake with an IC50 of 0 63 /AM. The presence of insulin receptors in human red blood cells, and the relationship between insulin and catecholamine levels in the plasma led us to investigate the effect of insulin on catecholamine transport. In fasting subjects, dopamine, adrenaline and noradrenaline influxes were higher than in fed subjects. Furthermore, the addition of exogenous insulin to red blood cells from fasting subjects significantly reduced the influx of catecholamines while no effect was observed when insulin was added to red blood cells obtained from fed subjects. The present study shows that catecholamines, and in particular dopamine, are transported in red blood cells via an exchanger which is possibly the choline transport system. The activity of this transporter is regulated by insulin. These results support a role for red blood cells as a storage pool for circulating catecholamines.

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