The effect of hypotensive therapy on the transcapillary escape rate of albumin 
(TERalb) was studied in eight hypertensive insulin-dependent diabetic patients 
(mean age 29, range 19-42 years) with nephropathy and retinopathy. 
Transcapillary escape rate of albumin (initial disappearance of intravenously 
injected 125I-labelled human serum albumin), urinary albumin excretion rate 
(radial immunodiffusion), and glomerular filtrate rate (single bolus 51-Cr-EDTA 
technique) were measured. After hypotensive treatment (mean duration, 23 months, 
range 7-39 months) with combinations of metoprolol, hydralazine, and frusemide 
or thiazide diuretics, arterial blood pressure fell from 152/103 +/- 18/6 mmHg 
(mean +/- SD) to 133/81 +/- 12/10 mmHg (p less than 0.01), transcapillary escape 
rate of albumin from 10.2 +/- 1.8 to 8.1 +/- 1.8% of intravascular mass of 
albumin/h (p less than 0.01), albuminuria from 1803 (370-5066) micrograms/min to 
940 (101-2676) micrograms/min (median and range, p less than 0.05), and 
glomerular filtration rate from 103 +/- 23 to 84 +/- 22 ml/min/1.73 m2 (p less 
than 0.01). Our study suggests that effective hypotensive treatment reduces the 
abnormally elevated albumin leakage characteristically found in 
insulin-dependent diabetic patients with clinical microangiopathy. This may be 
due to a reduction in the hydrostatic pressure in the microcirculation.