Increased rate of adenine incorporation into adenine nucleotide pool in erythrocytes of patients with chronic renal failure

Background: Elevated purine nucleotide pool (mainly ATP) in erythrocytes of patients with chronic renal failure (CRF) is a known phenomenon, however t he mechanism responsible for this abnormality is far from being clear. We h ypothesize that the increased rate of adenine incorporation into adenine nu cleotide pool is responsible for the elevated level of ATP in uremic erythr ocytes. Methods: In chronically uremic patients we evaluated using HPLC tec hnique: (a) plasma adenine concentration; (b) the rate of adenine incorpora tion into adenine nucleotide pool in uremic erythrocytes. Additionally, the effect of higher than physiological phosphate concentration (2.4 mM) and l ower than physiological pH (7.1) on adenine incorporation into erythrocytes adenine nucleotide pool was investigated. Healthy volunteers with normal r enal function served as control. Results: The concentration of adenine in p lasma of CRF patients was found to be significantly higher than in plasma o f healthy subjects. In contrast, adenosine concentration was similar both i n healthy humans and in CRF patients. In isolated erythrocytes of uremic pa tients (incubated in the medium pH 7.4, containing 1.2 mM inorganic phospha te) adenine was incorporated into adenine nucleotide pool at a rate approxi mately 2-fold higher than in erythrocytes from healthy subjects. The rate o f adenosine incorporation into adenine nucleotide pool was similar in eryth rocytes of both studied groups. Incubation of erythrocytes obtained from he althy subjects in the medium pH 7.4, containing 2.4 mM inorganic phosphate, caused the in crease of adenine incorporation into adenine nucleotide pool by about 60%. Incubation of the cells in the pH 7.1 buffer containing 2.4 mM inorganic phosphate increased the rate of adenine incorporation into ade nylate approximately 2-fold as compared to erythrocytes incubated in the me dium pH 7.4 containing 1.2 mM inorganic phosphate. Erythrocytes obtained fr om uremic patients and incubated in the pH 7.1 medium containing 2.4 mM pho sphate incorporated adenine into adenine nucleotide pool at a rate similar to erythrocytes incubated in the medium pH 7.4 containing 1.2 mM phosphate. Erythrocytes obtained from either healthy subjects or from patients with C RF and incubated in the presence of higher than physiological concentration of inorganic phosphate (2.4 mM) and lower than physiological pH (7.1) did not exhibit any increase in the rate of adenisine incorporation into adenin e nucleotide pool. Conclusion: These results suggest that the increased rat e of adenine incorporation into adenine nucleotide pool could be partially responsible for the increased concentration of ATP in uremic erythrocytes. Copyright (C) 2000 S. Karger AG, Basel.