Abstract
Transcapillary escape rates of albumin and IgG (fractions of intravascular mass of albumin and IgG that pass to the extravascular space per unit time) were determined simultaneously from the initial disappearance of intravenously injected 131I human albumin and 125I human IgG, in 10 long-term juvenile diabetics with microangiopathy (mean duration 20 years), and 9 non-diabetic subjects. Transcapillary escape rates of albumin (TERalb) and IgG (TERIgG) were found significantly increased in the long-term diabetic group, average 7.4 ± 1.1 (mean ± S.D.) and 4.4 ± 1.0 per cent/hour, respectively, compared to the non-diabetic group, mean 5.2 ± 1.0 and 3.0 ± 0.7 per cent/hour, respectively (p < 0.005). The TERIgG/TERalb ratio was nearly identical in the two groups, and very close to the ratio of the proteins' free diffusion coefficients. We assume that the present findings reflect an increased microvascular permeability to macromolecules, owing to an increased number or size of the large pores per unit surface area.