The use of PFC exchange transfused rats in studies of lung microvascular permeability.

The fluorocarbon exchange transfused rat was used to examine the effect of varying concentrations of circulating proteins on the permeability of pulmonary endothelium to inject ferritin. There is a significant inverse relationship between protein concentration and the relative number of vesicles containing ferritin as well as the amount of ferritin in the basement membrane. A hysteresis effect of the amount of circulating protein on the permeability of endothelium to ferritin was noted. In repletion experiments almost 2.5 times more protein was required to maintain capillary permeability at normal levels than during depletion experiments.