Endothelin-1 and Prostacyclin Attenuate Increases in Hydraulic Permeability due to Platelet-activating Factor in Rats

We have previously documented that endothelin-1 (ET-1) and prostacyclin (PGI 2 ) decrease basal state hydraulic permeability (L p ). The aim of this study was to investigate the ability of ET-1 and PGI 2 to modulate trans-endothelial fluid flux during situations in which L p was artificially elevated with platelet activating factor (PAF). We hypothesized that ET-1 and PGI 2 administration before PAF exposure would prevent the increase in L p secondary to PAF. Additionally, in a potentially more clinically relevant situation, we also hypothesized that ET-1 and PGI 2 administration after PAF exposure would attenuate the increase in L p secondary to PAF. Microvascular L p was measured in rat mesenteric post-capillary venules. Exposure to 10 nM PAF increased L p 4-fold (p