The increased production of endothelin-1 (ET-1) is associated with the disruption of the hepatic microcirculation in response to hepatic stress, often leading to portal hypertension due to increased portal venous resistance. Kupffer cell (KC) derived thromboxane A₂ (TXA₂), an arachidonic acid (AA) derived eicosanoid, mediates portal hypertension in the early development of fibrosis and the portal hyperresponsiveness to ET-1 during acute endotoxemia. Therefore, the purpose of the present study was to delineate the underlying mechanisms of ET-1 induced release of TXA ₂ during the development of fibrosis and associated portal hypertension compounded or uncompounded with acute endotoxemia. Using the one week bile duct ligation (BDL) induced portal hypertensive model of early stage fibrosis, our results suggest the elevated productions of TXA₂ and increased portal pressure (PP) during the early stages of fibrosis are mediated by the increased ET-1 induced activation of cytosolic phospholipase A₂ (cPLA₂) and arachidonic acid (AA) release due to modifications of ET-1 signaling, including increased Gi coupled ET(B) receptors and p38 MAPK kinase activity, in addition to upregulations of enzymes of AA metabolism and TXA₂ biosynthesis in KCs. The sequential stress of acute endotoxemia exacerbates the phosphorylation of cPLA₂ and subsequent release of AA which translates into significantly greater productions of TXA ₂, sustaining the BDL induced elevated portal venous pressure. Collectively, these studies provide significant interactions of ET-1 and TXA₂ during the pathogenesis of fibrotic liver disease often compounded with the enhanced translocation of endotoxin from the gut into the portal venous circulation and may provide further insight into potential therapeutic strategies for the prevention and treatment of chronic fibrotic liver disease. Furthermore, these data clearly demonstrate the significance of the activation of cPLA ₂ and production of TXA₂ in response to ET-1 in contributing to the increased vasoconstriction and subsequent increase in hepatic resistance, thereby potentially mediating portal hypertension.