Portal PressureHypertension, PortalSplanchnic CirculationLiver CirculationBlood CirculationLiver Cirrhosis, ExperimentalHemodynamicsLiver CirrhosisPortal SystemSepsisEndotoxemiaShock, SepticCardiac OutputMesenteric Artery, SuperiorVascular ResistanceLigationNitric OxideRegional Blood FlowRats, Sprague-DawleyPortal VeinBlood PressureExtracorporeal CirculationEpoprostenolNitric Oxide SynthaseBlood Flow VelocityPulmonary CirculationNitroarginineSheepVasodilationDisease Models, AnimalSyndromeTime FactorsLiverCollateral CirculationSwineEnzyme InhibitorsHeart RateEnterohepatic CirculationMyocardiumCoronary CirculationCerebrovascular CirculationPlacental CirculationBlood Circulation Time