tor, tumor necrosis factor, and other cytokines. 4 All of these To evaluate the role of nitric oxide (NO) in hepatic micromediators may be involved in the pathogenesis of liver injury, circulation and liver injury during endotoxemia, we studied probably initiated by microvascular disturbance caused by O 2 transport in the hepatic microcirculation of endotoxinleukocyte adhesion to endothelial cells in the hepatic sinuinfused rats. Rats were continuously infused with Escherichia soids. [5][6][7] Nitric oxide (NO) also increases during endotoxcoli lipopolysaccharide (LPS) (0.8 mg/kg/h) for 7 hours. LPS emia 8,9 and sepsis, 10 produced by Kupffer cells, macrophages, increased the plasma levels of NO 0 2 / NO 0 3 and aspartate hepatocytes, and sinusoidal endothelial cells. 9 Overproductransaminase (AST), and decreased the bile flow rate and tion of NO plays a toxic role in septic shock. 11 Peroxynitrite hepatic adenosine triphosphate (ATP) level. Hepatic microcirgenerated from superoxide and NO may be involved in sevculation was evaluated by two methods: reflectance spectroeral types of tissue injury. 12,13 On the contrary, NO attenuates photometry showed a decrease in the oxygenation of hemoglohepatic injury during endotoxemia. [14][15][16][17] Thus, the roles of bin (Hb) in the liver, and dual-spot microspectroscopy NO in endotoxemia are controversial. Nishida et al. recently indicated that LPS administration decreased blood velocity, reported that inhibition of NO synthesis in endotoxemia led the oxygenation of Hb, and O 2 release from sinusoids to hepato an increase in the leukocytes adhering to the sinusoidal tocytes. The observed decreases in the O 2 transport paramewall and a decrease in the number of sinusoids displaying ters were prominent in pericentral sinusoids. All of these blood flow. 5 These results imply a deterioration of O 2 transphenomena were further aggravated by the administration of port in hepatic microcirculation; however, there has as yet N w -nitro-L-arginine methyl ester (L-NAME) (5 mg/kg/h) plus been no experimental evidence of this.
LPS, and by aminoguanidine (AMG) (5 mg/kg/h) plus LPS,
Dual-spot microspectroscopy is useful for evaluating heand these could be reversed by the concomitant administrapatic microcirculation to quantify sinusoidal O 2 transport tion of L-arginine (L-Arg) (100 mg/kg/h). These results suggest parameters such as red blood cell velocity, intrasinusoidal that deterioration of hepatic oxygen transport and liver funchemoglobin (Hb) concentration, Hb oxygenation, and the tion induced by endotoxin can be ameliorated by NO. (HEPArate of O 2 transfer from sinusoids to hepatocytes. 18 In the TOLOGY 1997;26:336-342.)
present study, we used this method to quantitatively study periportal and pericentral sinusoidal O 2 transport in endo-Cholestatic liver injury is commonly observed in septic toxin-infused rat livers. patients. 1 Endotoxin, a major exogenous product of bacteria, causes similar morphological and functional alterations in MATERIALS AND METHODS the liver. 2 Because the addition of endotoxin to isolated hepatocytes has no effect on the release of aspartate transaminase Chemicals. Lipopolysaccharide (LPS) (Escherichia coli; Serotype (AST), 3 it is surmised that liver injury is not directly induced 0127: B8), N w -nitro-L-arginine methyl ester (L-NAME), and amino- by endotoxin. guanidine (AMG), inhibitors of NO synthesis, were purchased from Sigma Chemical Co. (St. Louis, MO). L-Arginine (L-Arg) was pur-Endotoxin activates endothelial cells, neutrophils, macrochased from Wako Chemical Co. (Osaka, Japan). All chemicals used phages, and Kupffer cells to produce platelet-activating facwere of analytical grade.
Animals. Male Sprague-Dawley rats weighing 250 to 300 g were used. The rats were provided with water and standard laboratory Abbreviations: AST, aspartate transaminase; Hb, hemoglobin; LPS, lipopolysacchachow ad libitum. All animal experiments were conducted in accorride; L-NAME, N w -nitro-L-arginine methyl ester; AMG, aminoguanidine; L-Arg, L-argidance with our institutional guidelines for the care and use of nine; iNOS, inducible nitric oxide synthase; ATP, adenosine triphosphate; Ihb, index laboratory animals. of blood volume in regional hepatic tissue; ISO2, index of blood oxygenation in regional Experimental Protocol. Rats were anesthetized with sodium pentohepatic tissue; So2, hemoglobin oxygenation; RO2, rate of oxygen release. barbital (40 mg/kg, intraperitoneally). A tracheotomy was per-From the