BACKGROUND: Microalbuminuria, a powerful predictor of cardiovascular events, is 
thought to reflect widespread subclinical vascular abnormalities. To explore the 
pathogenesis of increased urinary albumin excretion in primary hypertension we 
evaluated systemic capillary permeability and ambulatory blood pressure (BP) 
measurement in two groups of matched untreated patients with (n = 11) and 
without (n = 29) microalbuminuria.
METHODS: Albuminuria was measured as the mean of albumin-to-creatinine ratio 
(ACR) in three nonconsecutive first morning urine samples. Systemic capillary 
permeability was evaluated by transcapillary escape rate of albumin (TERalb) 
(ie, the 1-h decline rate of intravenous (125)I-albumin). Twenty-four-hour 
ambulatory BP, renal hemodynamics, and hormones of the 
renin-angiotensin-aldosterone system (RAAS) were also assessed.
RESULTS: Patients with microalbuminuria showed greater body mass index (BMI) (P 
< .04), higher 24-h systolic and diastolic BP levels (P = .02), and higher 
capillary permeability to albumin (P < .02) as compared to normoalbuminurics. 
Renal hemodynamics and RAAS hormones were similar in the two groups. Univariate 
analysis showed that urinary ACR was related to ambulatory pressure components 
(P < .02), TERalb (r = 0.31, P < .05), smoking habits (r = 0.36, P = .02), and 
left ventricular mass index (LVMI) (r = 0.57, P < .001) among the whole study 
group. Logistic regression analysis showed that each 1% increment in TERalb or 
10 mm Hg increase in systolic BP entailed an almost three times higher risk of 
having microalbuminuria.
CONCLUSIONS: Microalbuminuria is associated with greater systemic BP load and 
increased vascular permeability in patients with primary hypertension.