Stimulation by adenosine of adenine nucleotide turnover in isolated hepatocytes: evidence for a futile cycle between AMP and adenosine.

Abstract

Addition of adenosine to isolated rat hepatocytes, as well as to other liver preparations, provokes marked increases in the intracellular concentration of ATP and total adenine nucleotides (Chagoya de Sanchez et al., 1972; Lund et al., 1975; Wilkening et al., 1975), that are explained by the utilisation of adenosine by adenosine kinase. The present work was initiated as a search for a mechanism whereby the rate of degradation of the adenine nucleotide pool would adapt to an increased rate of synthesis. It led to the unexpected ascertainment that, under normal conditions, there is a continuous formation of adenosine by the hepatocytes. This production does, however, not contribute to the formation of allantoin but is part of a futile cycle operating between AMP and adenosine.