Futile cycle, between AMP and

Stimulation by Adenosine of Adenine Nucleotide Turnover in Isolated Hepatocytes Evidence for a Futile Cycle between AMP and Adenosine.475... 

STIMULATION BY ADENOSINE OF ADENINE NUCLEOTIDE TURNOVER IN ISOLATED HEPATOCYTES EVIDENCE FOR A FUTILE CYCLE BETWEEN AMP AND ADENOSINE... 

Lomax and Henderson (1973) have briefly alluded to the possibility that simultaneous breakdown and resynthesis of AMP may be a normal occurence in Ehrlich ascites tumor cells, and Arch and Newsholme (1978) have discussed the theoretical implications of this substrate cycle in detail. The discovery that the futile cycle between AMP and adenosine operates in isolated hepatocytes in basal conditions should provide further impetus for the study of its physiological significance. 

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 foriaation 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. 

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