Hypoxanthine production by ischemic heart demonstrated by high pressure liquid chromatography of blood purine nucleosides and oxypurines

An isocratic high pressure liquid Chromatographic system was developed for the estimation of purine nucleosides and oxypurines in blood. Use was made of a reversed-phase column. Nucleotides derived from erythrocytes affected the separation; these compounds were removed with Al₂O₃. The recovery of the whole clean-up procedure exceeded 75%, and the lower detection limit of the assay for blood metabolites was 0.1 μmol/l. In 6 healthy volunteers, non-resting, the following blood concentrations (mean values ± S.D. in μmol/l) were observed: adenosine (< 0.1), inosine (0.2 ± 0.1), hypoxanthine (2.2 ± 1.3) and xanthine (0.2 ±0.1). In plasma and serum the total amount of these compounds was 1.9 and 5.4 times higher, respectively, presumably due to nucleotide breakdown during blood processing. The myocardial arterial-venous differences of blood purine nucleosides, oxypurines and lactate were subsequently measured in blood samples from 13 patients with angiographically documented ischemic heart disease, undergoing an atrial pacing stress test. No significant release of adenosine, inosine and xanthine by the heart was detectable in this study. The myocardial arterial-venous difference of lactate changed from 0.01 ± 0.03 mmol/1 (mean ± SEM) at rest, to -0.10 ± 0.04 mmol/1 during pacing (p < 0.002). Relatively larger changes were observed for hypoxanthine: pacing increased the arterial-venous difference from -0.01 ± 0.05 to -0.51 ± 0.17 μmol/1 (p <0.02). We conclude that the high pressure liquid chromatographic assay of blood hypoxanthine is a useful tool in the diagnosis of ischemic heart disease.