Plasma concentrations of endothelial vasoactive substances in clinically healthy subjects. Associations with urinary albumin excretion and ambulatory blood pressure

Elevated urinary albumin excretion (UAE) is a predictor of cardiovascular disease, and one possible explanation is that elevated UAE reflects a generalized vascular dysfunction. The present study tests whether the plasma concentrations of the two main endothelial vasoactive substances (nitric oxide and endothelin-1 [ET-1]) are changed in clinically healthy subjects with elevated UAE (>6.6 microg/ min-the 90th percentile in the background population) and to test associations between these concentrations and systemic blood pressure. Twenty-seven subjects with elevated UAE were compared with 46 matched controls with normoalbuminuria. Plasma concentration of ET-1 was measured using an ELISA method and plasma concentration of nitrate/nitrite using a photometric method. Twenty-four-hour blood pressure was measured using a portable recorder (TM-2421). No significant differences in the concentrations of nitrate/nitrite and ET-1 were found between the groups, e.g. 21 (10-105) vs. 18 (11 -152) (p=0.33) and 0.98 (0.58 1.95) vs. 1.10 (0.54 -1.50) (p = 0.27), respectively. However, plasma nitrate/nitrite was significantly positively correlated to systolic and diastolic blood pressure in subjects with normoalbuminuria but not in subjects with elevated UAE. In contrast, plasma ET-1 concentration was significantly positively correlated to systolic blood pressure only in subjects with elevated UAE. In conclusion, elevated UAE is not associated with changed plasma concentrations of endothelial vasoactive substances in clinically healthy subjects. However, nitrate/nitrite is positively correlated to BP only in subjects with normoalbuminuria, and ET-1 is positively correlated to BP only in subjects with elevated UAE.