PPACK ATTENUATES PLASMIN-INDUCED CHANGES IN ENDOTHELIAL INTEGRITY

In order to determine whether plasmin affects endothelial cell integri ty directly, confluent bovine aortic endothelial cells were treated wi th plasminogen and a plasminogen activator. The permeability of the mo nolayer to [I-125]-albumin was shown to be increased significantly (P < 0.01) with a concomitant decrease in viability. Plasmin activity cor related significantly with endothelial cell permeability (p < 0.004; r = 0.82). Coincubation with D-phenylalanyl-L-prolyl-L-arginyl chlorome thylketone, a tripeptide inhibitor of plasmin, reduced the increase in endothelial permeability induced by plasmin by 59% (p = 0.033). Monol ayers studied in parallel were stained with rhodamine-phalloidin to vi sualize F-actin. There were significant morphologic changes in the end othelial monolayers exposed to plasmin compared to control monolayers, and these changes could be attenuated by coincubation with D-phenylal anyl-L-prolyl-L-arginyl chloromethylketone. These studies show that: 1 ) plasmin induces significant increases in endothelial cell permeabili ty with accompanying morphologic changes; and 2) these deleterious fun ctional and morphologic effects can be attenuated by coincubation with the plasmin inhibitor, D-phenylalanyl-L-prolyl-L-arginyl chloromethyl ketone.