BACTERIAL EXOTOXINS AND ENDOTHELIAL PERMEABILITY FOR WATER AND ALBUMIN INVITRO

Effects of Staphylococcus aureus .alpha.-toxin and Pseudomonas aeruginosa cytotoxin on the permeability of an endothelial monolayer were studied. Porcine pulmonary artery endothelial cells were grown on a polycarbonate membrane, mounted in a chamber, and exposed to a continuous hydrostatic pressure of 10 cmH2O. On application of this transendothelial pressure, endothelial monolayer became "sealed", i.e., the filtration rate for water decreased and the reflection coefficient for albumin increased, reaching a plateau after 1-2 h. Sealed monolayer had a hydraulic conductivity of 2.1 .times. 10-6 cm .cntdot. s-1 .cntdot. cmH2O and an albumin reflection coefficient of 0.73. Permeability of the monolayer was increased on addition of an excess of EDTA and reversed on readdition of calcium. Within 60-90 min after addition of 1 .mu.g/ml .alpha.-toxin, the filtration rate increased 75-fold, and the albumin reflection coefficient dropped to 0.20. These changes in permeability were accompanied by cell retraction and formation of large intercellular gaps between endothelial cells. Effects of .alpha.-toxin were abolished by preincubation with neutralizing antibodies and by inhibitors of calmodulin function. Pseudomonas aeruginosa cytotoxic (25 and 50 .mu.g/ml) also increased the permeability of the endotehlial monolayer, but it was only about one-third as effective as .alpha.-toxin.