Arginine is an important substrate in health and disease. It is a commonly held view that arginase-1 release from injured erythrocytes and hepatocytes leads to arginine breakdown; however, the true relationship between plasma arginase-1 concentration and activity has remained unaddressed. In the present study, blood was sampled from patients undergoing liver resection, a known cause of hepatocyte injury and arginase-1 release, to determine arginase-1, arginine and ornithine plasma levels. Arginase activity was assessed in vitro by measuring changes in arginine and ornithine plasma levels during incubation of plasma and whole-blood samples at 37 °C. Arginase-1 plasma levels increased 8–10-fold during liver resection, whereas arginine and ornithine levels remained unchanged. In accordance with these in vivo findings, arginine and ornithine levels remained unchanged in plasma incubated at 37 °C irrespective of the arginase-1 concentration. In contrast, arginine plasma levels in whole blood decreased significantly during incubation, with ornithine increasing stoichiometrically. These changes were irrespective of arginase-1 plasma levels and were explained by arginase activity present in intact erythrocytes. Next, plasma samples with 1000-fold normal arginase-1 concentrations were obtained from patients undergoing cadaveric liver transplantation. A significant decrease in arginine plasma levels occurred in vivo and in vitro. In contrast with commonly held views, moderately increased arginase-1 plasma levels do not affect plasma arginine. Very high plasma arginase-1 levels are required to induce potential clinically relevant effects.
Elevated plasma arginase-1 does not affect plasma arginine in patients undergoing liver resection
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Marcel C. G. van de Poll, Sebastiaan J. P. Hanssen, Maaike Berbée, Nicolaas E. P. Deutz, Diethard Monbaliu, Wim A. Buurman, Cornelis H. C. Dejong; Elevated plasma arginase-1 does not affect plasma arginine in patients undergoing liver resection. Clin Sci (Lond) 1 February 2008; 114 (3): 231–241. doi: https://doi.org/10.1042/CS20070143
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