Utilization of adenosine for nucleotide synthesis in the erythrocytes of some animals

Erythrocytes of human, monkey, dog, rat, mouse, guinea pig, hen, or frog were incubated with [U-14C]adenosine at a concentration of 0.23 muM, a level roughly corresponding to its plasma level in mammals. Direct utilization of adenosine by phosphorylation (the kinase pathway) and indirect utilization via hypoxanthine (the hypoxanthine pathway) were analyzed from the ratio of the specific radioactivities of nucleotide and base, as described previously (1,2). Both human and monkey cells efficiently utilized adenosine only by the kinase pathway, while rodent cells used the same route with an efficiency which varied with the species. Canine cells incorporated adenosine in extremely small amounts both by the kinase pathway and via the hypoxanthine pathway with a marked predominance of the former. Frog erythrocytes were similar to dog cells in mechanism of utilization, but the efficiency was of the same level as that of the primates. In contrast to other animals tested, the avian cells utilized twice as much adenosine via the hypoxanthine pathway as by the kinase pathway.