Uptake of Adenosine in Human Erythrocytes

Abstract

The transport of nucleosides across mammalian cell membranes is performed by a transport system with broad specificity for purine and pyrimidine nucleosides, For this uptake process a two comnonent system is discussed; one for low physiological and another for high concentrations of nucleosides (1, 2, 3). In human blood platelets a close association of the high affinity carrier for adenosine with adenosine kinase (AK, E. C. 2.7.1.20) was postulated, indicating phosphorylation being an integral part of adenosine transport as described in bacteria (3, 4). In contrast at high concentrations adenosine transported unchanged into the platelets and is then converted by adenosine deaminase (ADA, E. C. 3.5.4.4) and purine nucleoside Phosphorylase (PNP, E. C. 2.4.2.1) into inosine and hypoxanthine.