Available evidence indicates that poor metabolic control and raised blood 
pressure each accelerate the development of diabetic microangiopathy. 
Microangiopathy is associated with excess albumin deposition in capillary 
basement membranes and it has been suggested that increased extravasation of 
plasma constituents may lead to basement membrane thickening. We measured the 
transcapillary escape rate of albumin, an indicator of the rate of extravasation 
of intravascular albumin from the circulation per unit time, following 
intravenous injection of 125I-human serum albumin. We examined the independent 
effects on the transcapillary escape rate of albumin of non-ketotic poor 
metabolic control, hypertension and microangiopathy. We studied non-diabetic 
control subjects and diabetic patients, initially when in non-ketotic poor 
metabolic control and again when control had been improved. We also studied 
normotensive well-controlled diabetic patients without microangiopathy, 
normotensive well-controlled diabetic patients with microangiopathy, 
hypertensive well-controlled diabetic patients without microangiopathy and 
hypertensive well-controlled diabetic patients with microangiopathy. The 
transcapillary escape rate of albumin was similar in non-diabetic control 
subjects (5.5 +/- 0.7%/h) and in both Type 1 (5.3 +/- 1.2%/h) and Type 2 (5.1 
+/- 0.6%/h) normotensive diabetic patients without long-term complications. 
During poor metabolic control the transcapillary escape rate of albumin was 
significantly higher than in non-diabetic subjects (8.8 +/- 0.8%/h and 5.5 +/- 
0.7%/h respectively, p less than 0.01). With improved control values fell 
significantly to 6.3 +/- 0.9%/h (p less than 0.02), not significantly different 
from control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)