Glycine minimizes reperfusion injury in a low-flow, reflow liver perfusion model in the rat.
This study investigated the effects of glycine on reperfusion injury in a low-flow, reflow liver perfusion model. With this protocol, livers were perfused at low flow rates of approximately 1 ml.g-1. min-1 for 75 min, which caused cells in pericentral regions of the liver lobule to become anoxic because of insufficient delivery of oxygen. When normal flow rates (approximately 4 ml.g-1.min-1) were restored for 40 min, an oxygen-dependent reperfusion injury occurred. Upon reflow, lactate dehydrogenase (LDH), a cytosolic enzyme, and malondialdehyde (MDA), an end product of lipid peroxidation, were released into the effluent perfusate. LDH increased from basal levels of approximately 1-35 IU.g-1.h-1 in livers from control rats. Glycine (0.06-2.00 mM) minimized enzyme release in a dose-dependent manner (half-maximal decrease = 133 microM), with maximal values only reaching 5 IU.g-1.h-1 when glycine was increased to 2 mM. Reflow for 40 min after 75 min of low-flow hypoxia caused death in approximately 30% of previously anoxic parenchymal cells in pericentral regions; however, infusion of glycine (2 mM) decreased cell death to less than 10%. Strychnine (1 mM), which was found to mimic the cytoprotective effect of glycine in proximal renal tubules, also reduced LDH release to 11 IU.g-1.h-1 in this study. Bile was released at rates of approximately 42 microliters.g-1.h-1 in livers from control rats, but values were not altered significantly by glycine. Maximal MDA production during reperfusion decreased by 35% with 0.6 mM of glycine. Trypan blue distribution time, an indicator of hepatic microcirculation, was reduced significantly by glycine at 5 and 40 min after reflow, but changes were about twofold greater at later time points compared with earlier ones (half-maximal decrease = 225 microM). Time for oxygen to reach steady state upon reflow was reduced by glycine in a dose-dependent manner, and the rates of entry and exit of a dye confined to vascular space (fluorescein dextran) were increased two- to threefold by glycine, respectively. Taken together, these data indicate that a reperfusion injury that occurs in previously hypoxic pericentral regions of the liver upon reintroduction of oxygen is minimized by glycine, possibly by action on a glycine-sensitive anion channel to improve microcirculation during the reperfusion period.
Zhong
Z
Z
Department of Pharmacology, University of North Carolina at Chapel Hill 27599-7365, USA.
Jones
S
S
Thurman
R G
RG
D000818:Animals; D005998:Glycine / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000473:pathology; D008102:Liver Circulation / Q000187:drug effects; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D008833:Microcirculation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000473:pathology / Q000517:prevention & control*; D013331:Strychnine / Q000494:pharmacology
D008315:Malondialdehyde; D013331:Strychnine; D005998:Glycine