Effects of fructose on synthesis and degradation of purine nucleotides in isolated rat hepatocytes.

The effects of fructose on purine nucleotide synthesis and degradation were studied in isolated rat hepatocytes. Incubation of the hepatocytes with fructose resulted in deceleration of the rate of de novo purine synthesis, gauged by the rate of incorporation of precusor [14C]formate into total purines produced, and in acceleration of purine nucleotide degradation, as measured by the rate of conversion of prelabelled purine nucleotides into end-product allantoin. These effects were found to be associated with decreases in cellular content of ATP and Pi and in the metabolic availability of 5-phosphoribosyl 1-pyrophosphate. The results support the suggestion that the fructose-induced acceleration of purine degradation is mediated through activation of AMP deaminase. However, the results also suggest that decreased reutilization of hypoxanthine for IMP synthesis, due to the decreased PP-Rib-P availability, is an additional mechanism for the acceleration of purine degradation. The decreased PP-Rib-P availability is also suggested to be the main mechanism for the fructose-induced deceleration of purine synthesis.