Accelerated degradation of adenine nucleotide in erythrocytes of patients with chronic renal failure

Recently, we have shown that erythrocytes obtained from patients with chron ic renal failure (CRF) exhibited an increased rate of ATP formation from ad enine as a substrate. Thus, we concluded that this process was in part resp onsible for the increase of adenine nucleotide concentration in uremic eryt hrocytes. There cannot be excluded however, that a decreased rate of adenyl ate degradation is an additional mechanism responsible for the elevated ATP concentration. To test this hypothesis, in this paper we compared the rate of adenine nucleotide breakdown in the erythrocytes obtained from patients with CRF and from healthy subjects. Using HPLC technique, we evaluated: (1) hypoxanthine production by uremic R BC incubated in incubation medium: (a) pH 7.4 containing 1.2 mM phosphate ( which mimics physiological conditions) and (b) pH 7.1 containing 2.4 mM pho sphate (which mimics uremic conditions); (2) adenine nucleotide degradation (IMP, inosine, adenosine, hypoxanthine production) by uremic RBC incubated in the presence of iodoacetate (glycolysis inhibitor) and EHNA (adenosine deaminase inhibitor). The erythrocytes of healthy volunteers served as cont rol. The obtained results indicate that adenine nucleotide catabolism measured a s a hypoxanthine formation was much faster in erythrocytes of patients with CRF than in the cells of healthy subjects. This phenomenon was observed bo th in the erythrocytes incubated at pH 7.4 in the medium containing 1.2 mM inorganic phosphate and in the medium which mimics hyperphosphatemia (2.4 m M) and metabolic acidosis (pH 7.1). The experiments with EHNA indicated tha t adenine nucleotide degradation proceeded via AMP-IMP-Inosine-Hypoxanthine pathway in erythrocytes of both patients with CRF and healthy subjects. Io doacetate caused a several fold stimulation of adenylate breakdown. Under t hese conditions: (a) the rate of AMP catabolites (IMP + inosine + adenosine + hypoxanthine) formation was substantially higher in the erythrocytes fro m patients with CRF; (b) in erythrocytes of healthy subjects degradation of AMP proceeded via IMP and via adenosine essentially at the same rate; (c) in erythrocytes of patients with CRF the rate of AMP degradation via IMP wa s about 2 fold greater than via adenosine. The results presented in this paper suggest that adenine nucleotide degrada tion is markedly accelerated in erythrocytes of patients with CRF.