The nucleic acid metabolism of animal cells in vitro: III. Factors influencing nucleotide biosynthesis

Abstract

In the Ehrlich ascites carcinoma of the mouse the rate of purine biosynthesis in vitro under aerobic conditions is greatly increased if the cells are supplied with glucose or uridine, although neither compound appears to increase the energy available to the cells. Glucose and nucleosides also increase the rate at which the cells take up adenine and uracil from the medium and convert them to nucleotides. Glucose has no effect on uptake of glycine and phenylalanine under anaerobic conditions, although it increases phenylalanine uptake when the cells are incubated under nitrogen. The L5178Y mouse ascites lymphoma differs from the Ehrlich ascites carcinoma in having a much higher content of glucose in vivo, a lower capacity for glucose uptake in vitro, and a higher capacity for purine nucleotide biosynthesis in vitro. In rabbit bone marrow, purine nucleotide biosynthesis in vitro is slow relative to nucleic acid biosynthesis, is not affected by the presence of glucose, and is only slightly increased by a mixture of glucose, glutamine, aspartic acid and glycine. It differs from the corresponding process in the ascites carcinoma in continuing at a steady rate for a longer period, and in being more sensitive to the inhibitory effects of azaserine. Chick embryo brain and skeletal muscle also synthesize purine nucleotides relatively slowly in vitro. In the latter, but not the former, the synthesis is accelerated by a mixture of glucose and glutamine.