Metabolic effects of glucose deprivation and of various sugars in normal and transformed fibroblast cell lines

Abstract

The sugar composition of the growth medium influenced the NAD + NADH ratio, pyruvate and lactate production, and ATP levels in both normal and transformed fibroblast cell lines growing in tissue culture. Removal of glucose led to a rapid three- to fourfold rise in the NAD + NADH ratio, followed by a slower decline in the content of ATP. However, there was no change in the adenylate energy charge [ ( ATP + 1 2 ADP)/( ATP + ADP + AMP ) ] over a 2-h period. The NAD + NADH ratio was restored to the original level within 10 s of glucose readdition. The NAD + NADH ratios in cell lines growing on galactose were as high as for those incubated without sugars; growth on mannose or fructose produced intermediate ratios. There was an inverse relationship between the NAD + NADH ratio and pyruvate-lactate production for glucose, fructose and galactose. Thus, all cell lines had a high production of pyruvate and lactate but a low NAD + NADH ratio when grown on glucose. In contrast, when galactose served as the sugar source, acid production was low, while the ratio was high. All cell lines had comparable hexokinase activity, and glucose was the best substrate, mannose intermediate and fructose poorest. Hexokinase activity did not correlate with the relative degree of utilization of the sugars. These results suggest that the sugar composition of the growth medium affects the metabolic pattern of a cell line, including the NAD + NADH ratio, the ATP content and the production of pyruvate and lactate.