Impaired renal functional reserve and albuminuria in essential hypertension.

The stimulatory effects of an infusion of amino acids on glomerular filtration rate has previously been used to measure renal functional reserve and detect glomerular hyperfiltration. Thirty four patients with mild to moderate essential hypertension and seemingly normal renal function and 22 healthy controls were given infusions of amino acids to investigate whether renal functional reserve is reduced in essential hypertension and to detect patients at risk of renal damage. Although basal creatinine clearance increased after the infusion of amino acids in the controls (mean 27.9 ml/min; 95% confidence interval 18.2 to 37.6), the overall change was lower in the patients (mean 13.4 ml/min; 8.3 to 18.5), 11 of the 34 showing no increase at all. In these 11 non-responders the mean systolic blood pressure was higher than that in the 23 others (178.5 mmHg v 157 mmHg, respectively). Mean urinary albumin excretion was abnormal in the patients (93.3 mg/24 h; 44.2 to 142.4); eight of the 11 non-responders had an albumin excretion above the normal range (greater than 20 mg/24 h). In the 11 patients without renal functional reserve a positive correlation was found between basal creatinine clearance and albumin excretion (r = 0.695). As consumed renal reserve and albuminuria are markers of glomerular hyperfiltration studying renal function before and after infusion of amino acids can detect hypertensive patients at risk of progressive renal damage.