TNF-induced permeability across EC monolayers is dependent on factor VIII–deficient plasma.

Permeability across functional EC monolayers was determined by measuring absorbance at 620 nm 1 hour following TNF treatment for 90 minutes as described in “Materials and methods.” TNF in the range of 1 μg/mL to 100 pg/mL did not result in any increase in permeability under basal culture conditions (A). However, TNF induced a rapid and significant increase in permeabiliity in the presence of factor VIII–deficient plasma and was partially blocked by AT III (B). Permeability was unaffected by factor VIII–deficient plasma, AT III, or TNF alone. Each value is the mean ± SD of triplicates in one representative experiment.