Interrelations of Diet-induced Changes in Hexosemonophosphate Shunt Dehydrogenases with RNA Metabolism in Rat Liver Slices ,

Abstract

The relationship of changes in hexosemonophosphate shunt dehydrogenase activity to RNA metabolism in response to fasting and fasting-refeeding a high carbohydrate protein-free diet or a high protein carbohydrate-free diet was investigated in rat liver slices. Starvation for 48 hours did not change hexosemonophosphate shunt dehydrogenase activity but resulted in a significant decrease in liver RNA content. When a high carbohydrate protein-free diet was refed for 48 hours, the dehydrogenease activity did not change and the pattern of incorporation of glucose-1, glucose-2, and glucose-6-14C into acid-soluble nucleotides indicated relatively little use of the oxidative part of the hexosemonophosphate shunt pathway for ribose synthesis. While the RNA content of the liver under this regimen remained unchanged from fasting levels, the rate of incorporation of radioactive precursors into RNA was restored to control untreated values.When a high protein carbohydrate-free diet was refed, increased levels of the hexosemonophosphate shunt dehydrogenase activity were observed. The pattern of incorporation of glucose carbon into acid-soluble nucleotides under these conditions suggested an increase in ribose formation by way of the oxidative portion of the hexosemonophosphate shunt dehydrogenase pathway. The nucleic acid content of the liver of this group was not different from that of control untreated rats. The results are discussed in relation to the dietary control of alternative pathways of pentose production for nucleic acid synthesis.