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Different patterns of arginine level and arginase activity in blood serum of patients with acute pancreatitis and pancreatic cancer

Arginase (EC 3.5.3.1.) is an enzyme that is found mainly in the liver, where it catalyzes the final reaction in the synthesis of urea. The enzyme is also present in other human tissues and in blood serum. Its substrate, arginine is involved in a variety of physiological and pathological processes, including biosynthesis of nitric oxide and polyamines – compounds that play important role in cell proliferation and differentiation, Cancer and inflammatory states are the most prevailing pancreatic illnesses. Earlier studies from our laboratory have shown that serum arginase activity is low in healthy persons and rises significantly in patients with pancreatic cancer (with specificity and sensitivity similar to those observed for Ca 19-9). Arginase activity is also increased in blood serum of patients with acute pancreatitis. However there are no available studies comparing arginine level and arginase activity in blood serum of patients with acute pancreatitis and pancreatic cancer. The aim of this study was comparison of arginine level and arginase activity in blood serum of patients with acute pancreatitis and pancreatic cancer. Arginase activity and arginine level were studied in blood serum of patients with acute pancreatitis (n=30) before and after treatment and those with pancreatic cancer before surgery (n=15). The control group included healthy blood donors. Arginase activity was determined according to Chinard (J Biol Chem, 1952, 199:91-95). Arginine level was assayed from the amount of ornithine formed by standardized arginase preparation (Clin. Chim. Acta 1980, 106:333-337). The increase in arginase activity was observed in both studied groups of patients, but it was more pronounced in pancreatic cancer compared to those with acute pancreatitis. The enzyme activity was lower after an effective treatment of pancreatic inflammation. Arginine level was decreased in patients with acute pancreatitis but increased in those with pancreatic cancer. In patients with acute pancreatitis an increased serum arginase activity coincided with lowered arginine concentration. Depletion of serum arginine may reflect both an impaired systemic synthesis of this amino acid and enhanced degradation due to increased arginase activity in the blood. Determination of arginase activity and arginine level in blood serum may be used as an adjunct test for evaluation of therapeutic outcomes in patients with acute pancreatitis. Conversely, in patients with pancreatic cancer an increased serum arginase activity was associated with increased arginine concentration. It suggests there is mechanism by which tumor cells affect arginine metabolism to maintain adequate systemic pool of this amino acid in spite of increased arginase activity. Further studies are needed to evaluate the mechanism of tumor effect on systemic arginine metabolism.

arginine; arginase; acute pancreatitis; pancreatic cancer

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