Measurement of hepatic microvascular endothelial function in rats

Objective To establish a method to evaluate the hepatic microvascular endothelial function in rats. Methods Twentyfour adult male Wistar rats were randomly divided into sham group and three ischemic groups with 1 h, 2 h and 3 h of liver ischemia (OPT 1 h, OPT 2 h and OPT 3 h). After reperfusion at different time points, the hepatic microcirculatory blood flow was measured. The hepatic microvascular endothelial function was assessed by local heating stimulation assay and post occlusive reactive hyperemia (PORH) assay. Results The baseline hepatic microcirculatory blood flow in normal rats was (198.30±8.98) PU. After local heating stimulation, the blood flow increased to (239.30±9.84) PU. In PORH assay of normal rat, the values of microcirculatory liver blood flow at baseline, post occlusion and hyperemia were (204.40±11.80) PU, (94.43±29.26) PU and (268.90±22.16) PU, respectively. After ischemia and reperfusion, the liver microcirculatory blood flow of OPT 1 h, OPT 2 h and OPT 3 h groups at baseline and post heating were significantly lower than those of sham group (P< 0.05), and it was significantly lower in OPT 3 h group than OPT 1 h group (P< 0.01) and OPT 2 h group (P< 0.05). After calculating the heating-induced increase of microcirculatory liver blood flow (Δ PU) of each group, we found that the Δ PUs of OPT1h group at 60 min and 90 min after reperfusion were significantly higher than those of sham group(57.33±4.63) PU vs (31.40±4.80) PU, (50.30±1.76) PU vs (30.00±4.41) PU, P< 0.05. The Δ PU of OPT 3 h group at 60 min was significantly lower than those of sham and OPT 1 h group (P< 0.05). In PORH assay, the PF-BZ values of OPT 2 h and OPT3h groups were (91.31±4.48) PU and (26.92±9.43) PU, which were significantly lower than those of sham and OPT 1 h group(187.32±15.00) PU and (144.90±9.94) PU, P< 0.05, and it was lower in OPT 3 h group than OPT 2 h group (P< 0.05). Conclusion The microvasculature of rat liver can respond to local heating stimulation and PORH. Prolonged ischemia and reperfusion may result in the dysfunction of microvascular endothelia, and local heating stimulation assay and PORH assay can be used to evaluate the hepatic microvascular endothelial function.