Ischemia/reperfusion induces an increase in the hepatic portal vasoconstrictive response to endothelin-1

Microvascular impairment observed during reperfusion following ischemia (IR) is a major determinant of the development of liver injury. Previous studies have shown that hyper-responsiveness to endothelin-1 (ET-1) contributes to microvascular dysfunction following a primarily inflammatory stress induced by endotoxin. The present study investigates whether a similar hypercontractile response to ET-1 occurs in the hepatic portal system of IR rats. Pentobarbital-anesthetized Sprague-Dawley rats underwent liver ischemia of the left and medial lobes for 60 min (IR: n = 8) or a sham operation (n = 8). Six hours after reperfusion, the liver was isolated and perfused through the portal vein. Baseline portal pressure (Pp), portal flow (Qp), and sinusoidal diameter (Ds) were measured before and 3 and 10 min after adding ET-1 (1 nM). In baseline, IR livers had a significantly greater Pp, portal resistance, and Ds than sham. ET-1 significantly increased Pp and portal resistance and significantly decreased Qp and Ds in IR and sham rats. However, these effects were significantly greater in IR. The results of the present study demonstrate that IR increases the porto-hepatic contractile response to ET-1, which may further sensitize the portal circulation to elevated ET-1 and may be a prominent contributor to the development of microvascular impairment following IR.