Diabetic patients with elevated urinary albumin excretion rate (incipient or 
clinical nephropathy) also have an increased transcapillary escape rate of 
albumin. This study was designed to clarify whether this is caused by a general 
vascular dysfunction or by elevated systemic blood pressure. The systemic blood 
pressure and the transcapillary escape rate of albumin were measured in the 
following groups after 4 weeks without antihypertensive treatment: Group 
1--eleven healthy control subjects. Group 2--ten Type 1 (insulin-dependent) 
diabetic patients with incipient nephropathy (urinary albumin excretion rate: 
30-300 mg/24 h) and normal blood pressure. Group 3--eleven non-diabetic patients 
with essential hypertension. Group 4--nine Type 1 diabetic patients with 
hypertension but normal urinary albumin excretion (< 30 mg/24 h). Group 
5--eleven Type 1 diabetic patients with nephropathy (urinary albumin excretion 
rate > 300 mg/24 h) and hypertension. Systolic and diastolic blood pressure were 
similar in the three hypertensive groups: group 3, 148 +/- 8/95 +/- 6; group 4, 
150 +/- 12/94 +/- 8 and group 5; 152 +/- 12/92 +/- 7 mmHg, but significantly 
elevated (p < 0.001) compared to control group 1, 117 +/- 12/74 +/- 9 and group 
2, 128 +/- 7/82 +/- 4 mmHg. The transcapillary escape rate of albumin was 
similar in the control subjects (5.2 +/- 2.7%) and the subjects in the 
normoalbuminuric groups 3 and 4 (6.2 +/- 1.9 and 5.1 +/- 1.4%, respectively) and 
significantly lower (p < 0.001) than in patients with elevated urinary albumin 
excretion without or with hypertension group 2, 10.1 +/- 2.8 and group 5, 11.4 
+/- 5.7%.(ABSTRACT TRUNCATED AT 250 WORDS)