Transcapillary filtration of plasma protein in long-term type 1 (insulin dependent) diabetic patients

To study the pathophysiologic mechanism leading to increased transcapillar sieving of albumin in patients with diabetic nephropathy, subcutaneous interstitial concentrations of albumin, transferrin, total IgG and IgG-4 was measured in 30 long-term type 1 diabetic patients using the skin suction blister method. Eight normal subjects served as controls. The patients were divided in groups according to their urinary albumin excretion: normal (n = 11), micro-albuminuria (n = 9), and clinical nephropathy (n = 10). Results were expressed as the blister to serum concentration ratio (Cb:Cs) of each macromolecule. Normoalbuminuric patients had lower Cb:CsIgG ratio than healthy controls (0.28 +/- 0.04 vs. 0.35 +/- 0.09, p = 0.03). The lowest Cb:CsIgG ratio (0.23 +/- 0.07) was found in patients with clinical nephropathy. The same trend could be demonstrated in the other Cb:Cs ratios, but differences there were not significant. No differences related to capillary charge- or size-selectivity could be demonstrated between the groups. The results might reflect an increase of intracapillary hydrostatic pressure or increased capillary hydraulic permeability in the diabetic state per se, augmented during the development of microvascular complications.