Microvascular protein leakage in extensive skin diseases: aspects of the transport mechanisms.

The transcapillary escape rates of albumin (TERalb) and IgG (TERIgG) (i.e. fractions of intravascular masses of albumin and IgG passing to the extravascular spaces per unit time) can be used as parameters of the microvascular leakiness to macromolecules. These parameters were examined simultaneously in 12 patients with extensive skin disease. Six of the patients were reexamined after treatment with systemic steroid. The significantly increased (p less than 0.001) pretreatment values of both TERalb and TERIgG were normalized after treatment with systemic steroid to mean values comparable to those of the control group (p greater than 0.1). The patients mean ratio of TERIgG/TERalb did not differ from that of controls, neither before nor after treatment (p greater than 0.1). The microvascular leakage to differently sized macromolecules in the patients examined seems to be independent of the underlying skin disease. On the background of the structural microvascular changes often described in inflammatory reactions developed experimentally, and the similar changes present in the microvasculature of the psoriatic skin, it is suggested, that the increased microvascular leakage as found in this study, is confined to the postcapillary venules. The functional mechanisms dominating the transport of macromolecules across the vessel wall in this study are compatible with free diffusion as well as with filtration.