Microalbuminuria and transcapillary albumin leakage in essential hypertension

Microalbuminuria (an increased urinary albumin excretion that is not detect able by the usual dipstick methods for macroproteinuria) predicts cardiovas cular events in essential hypertensive patients. A possible reason for this behavior is that albumin leaks through exaggeratedly permeant glomeruli ex posed to the damaging impact of subclinical atherogenesis. To evaluate this possibility, the transcapillary escape rate of albumin (TERalb, the 1-hour decline rate of intravenous I-125-albumin), a parameter that estimates the integrity of systemic capillary permeability, albuminuria, blood pressure, echocardiographic left ventricular mass, lipids, and body mass index were measured in 73 uncomplicated, glucose-tolerant men with essential hypertens ion and normal renal function; 53 were normoalbuminuric, and 20 were microa lbuminuric. Twenty-one normotensive age-matched male subjects were the cont rols. TERalb was higher in hypertensives, a behavior explained in part by a positive correlation with blood pressure values, although body mass index, lipids, and left ventricular mass showed no association. Transcapillary al bumin leakage values did not differ between normoalbuminuric and microalbum inuric patients and were unrelated to albuminuria. Blood pressure, particul arly systolic, and cardiac mass were higher in microalbuminuric patients in whom albuminuria correlated with both cardiovascular variables and indicat ed the influence of the hemodynamic load on urinary albumin levels. Thus, T ERalb, a parameter influenced by the permeability surface area product for macromolecules and the filtration power across the vascular wall, is altere d in essential hypertensives. However, this abnormality is dissociated from the amount of albuminuria, which is contrary to the hypothesis that a high er albumin excretion reflects a greater degree of systemic microvascular da mage in essential hypertension.