Effect of lipopolysaccharides on erythrocyte flow velocity in rat liver

Although endotoxin exacerbates hepatic microcirculatory disturbance, little is known of the way in which it acts on the hepatic microcirculation. We measured endotoxin-induced changes in hepatic microcirculation and investigated the effect of endotoxin on hepatic microcirculation in rats. After male Wistar rats were anesthetized, a lobe of the liver was observed with an inverted intravital microscope. Erythrocytes (RBC) were labeled with fluorescein isothiocyanate (FITC) and injected. The flow velocity (FV) of FITC-RBC in sinusoids was measured with an off-line velocimeter. Portal pressure (PP) and mean arterial pressure (MAP) were measured with a catheter cannulated in the portal vein and the left carotid artery, respectively. After a small dose (1 mg/kg) of endotoxin had been administered intravenously, FV decreased and PP increased gradually after 30 min. MAP showed no significant change, except for an initial decrease. However, when 5 mg/kg of endotoxin was administered, FV and PP increased, with a peak at 10 min, which was not observed with the small dose. In the late phase, FV decreased and PP increased, as was seen with the small dose. Endotoxin increased serum aspartate aminotransferase and lactate dehydrogenase activities. These results suggest that endotoxin induces hepatic microcirculatory disturbance, which may cause liver injury.