We previously reported that nitric oxide (NO) derived from endothelial NO synthase (NOS) increased endothelial prostacyclin (PGI₂) production in rats subjected to hepatic I/R. The present study was undertaken to determine whether neutrophil elastase (NE) decreases endothelial production of PGI₂, thereby contributing to the development of ischemia/reperfusion (I/R)-induced liver injury by decreasing hepatic tissue blood flow in rats. Hepatic tissue levels of 6-keto-PGF₁, a stable metabolite of PGI₂, were transiently increased and peaked at 1 h after reperfusion, followed by a gradual decrease until 3 h after reperfusion. Sivelestat and L-658, 758, two NE inhibitors, reduced I/R-induced liver injury. These substances inhibited the decreases in hepatic tissue levels of 6-keto-PGF₁ at 2 and 3 h after reperfusion, but did not affect the levels at 1 h after reperfusion. These NE inhibitors significantly increased hepatic tissue blood flow from 1 to 3 h after reperfusion. Both hepatic I/R-induced increases in the accumulation of neutrophils and the microvascular permeability were inhibited by these two NE inhibitors. Protective effects induced by the two NE inhibitors were completely reversed by pretreatment with L-nitro-arginine-methyl-ester, an inhibitor of NOS, or indomethacin. Administration of iloprost, a stable derivative of PGI₂, produced effects similar to those induced by NE inhibitors. These observations strongly suggested that NE might play a critical role in the development of I/R-induced liver injury by decreasing endothelial production of NO and PGI₂, leading to a decrease in hepatic tissue blood flow resulted from inhibition of vasodilation and induction of activated neutrophil-induced microvascular injury.