Background: Arginine is an amino acid having a central role in the metabolism of urea and nitric oxide in the liver. We present our findings of the behavior of these metabolites during the process of transplantation of the liver.
Methods: Urea, arginine, ornithine, citrulline, gamma-aminobutyric acid, glutamate, and glutamine levels in 15 livers were studied during the process of retrieval, following storage during the backtable procedure, and for 48 hours postreperfusion using microdialysis. Arginase levels in donor and recipient serum were also analyzed using an enzyme-linked immunosorbent assay specific for type I human arginase. Data was analyzed using one-way analysis of variance, with post-hoc comparison to the value at two hours using Dunnett's test (P < 0.05 significant).
Results: Levels of metabolites measured in the donor liver were seen to decline significantly in the stored liver. Immediately postreperfusion, there was a significant rise in arginase I levels in the recipient serum with low arginine levels recorded in the liver. The high arginase I levels significantly reduced six hours postreperfusion with a corresponding rise in extracellular arginine levels. Urea levels in the graft increased significantly immediately postreperfusion.
Conclusions: Arginine levels were found to be low with correspondingly high serum arginase I levels in the early postreperfusion phase. High serum arginase I levels in early postreperfusion may influence nitric oxide production in this phase since considering Vmax and Km values, arginase I could compete with inducible nitric oxide synthase for arginine. Urea metabolism in the liver recommences immediately postreperfusion.