The concentrations of albumin, transferrin, IgG and α₂-macroglobulin were measured in serum (C₈) and in blister fluid (C_b) from lesional skin obtained by suction in 11 patients with extensive skin disease. The results were compared with those of 10 matched control subjects. In the patients the C_b/C₈ ratios and the distribution ratios (i.e., intravascular to total masses) of the 4 proteins and that of inulin were correlated to the corresponding molecular weights. The distribution ratios of the proteins were calculated from plasma volume (PV), C₈, C_b and extracellular fluid volume (ECV) determined with inulin, and that of inulin as PV/ECV.

The distribution ratio of albumin was similar to that obtained from a long-term metabolic turnover study.

It is concluded that the sieving properties of the dermal vascular endothelium is maintained during suction also in patients with extensive skin disease and that the blister fluid equals “average” interstitial fluid.

The transcapillary escape rate (TER) of albumin and IgG (i.e., fractions of intravascular masses of albumin and IgG passing to the extravascular space per unit time) and the accumulation rate of i.v. injected ¹³¹I human serum albumin and ¹²⁵-IgG in the blister fluid was significantly increased in the patients. The latter was increased 2 to 3-fold. It is shown, that the increased extravasation of plasma proteins from the skin microvasculature accounts fully for the increased escape rates as measured in whole man, of albumin as well as IgG.