P6.11 RELATIONSHIPS BETWEEN ENDOTHELIAL FUNCTION, ARTERIAL ELASTICITY AND BAROREFLEX SENSITIVITY

Abstract

Endothelium derived nitric oxide (NO) increases conduit artery distensibility, through relaxation of vascular smooth muscle. Barosensory wall distensibility influences the mechanical component of baroreflex sensitivity (BRS) by modifying the baroreceptor stimulus. NO bioavailability may also affect the neural component of BRS, by influencing afferent sensitivity, central neural processing or neuroeffector mechanisms. We aimed to study the relationships between the above variables in young healthy volunteers (n=28, male:female 10:18; age 16.5±1.4 years). To this end we measured brachial artery endothelial function by brachial flow mediated dilatation normalized with peak mean shear rates (nFMD) and carotid artery biomechanical parameters and blood pressure by ultrasonographic wall-tracking and tonometry. From these variables elastic parameters were calculated. BRS was measured by the spontaneous sequence method (Seq+). The mean values (mean±SD) were 5.41±1.49 [10−3/mmHg] and 4.79±1.14 for carotid artery distensibility coefficient and stiffness index β, respectively, 2.59±1.00 for nFMD and 25±16 [ms/mmHg] for Seq+. Using correlation and linear regression analysis, we found that elastic parameters were not related, but BRS was significantly related to nFMD (r=0.486, p<0.05). However, the correlation was limited only to males (r=0.681p<0.05 vs. r=0.368p=0.133, females). Our results suggest that the positive correlation between endothelial function and BRS can not be explained by the mechanical vessel wall properties. This association may be due to neural mechanisms transmitted by NO. The gender differences and the relationship between endothelial function and the neural component of the BRS need further studies.