Comparative studies of glucose‐fed and glucose‐starved hamster cell cultures: Responses in galactose metabolism

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Abstract
The metabolic flow of trace amounts of D‐[14C]‐galactose was followed in cultures of transformed and untransformed hamster cells over a period ranging from five minutes to two hours. The results of chromatographic and enzymatic analyses of the soluble pools are described. Non‐glycolytic cells (previously deprived of sugar for periods of up to 24 hours) convert D‐galactose to galactose‐1‐phosphate and uridine diphosphoglucuronic acid in 10 to 20 minutes. In the same short assay time, glycolytic cells which have been maintained for 24 hours in media containing glucose or galactose convert D‐galactose to uridine diphosphogalactose and uridine diphosphoglucose (ratio 1.4:1). Longterm deprivation of sugar also results in 3‐ to 4‐fold increases in the uptake of galactose. In addition, the incorporation of galactose label into chloroform‐methanol soluble material appears to be influenced by the culture conditions of the untransformed cells while incorporation in the transformed cells appears unaffected. When cycloheximide is included in the maintenance medium for extended periods, the non‐glycolytic cells also show increases in galactose uptake rates but the glucose‐fed, glycolytic cells lose uptake ability. UDPhexose is the main galactose metabolic peak in the soluble pools of the cycloheximide‐treated, glycolytic and the cycloheximide‐treated, non‐glycolytic cells. The results of these experiments suggest that uptake of galactose and its subsequent metabolism are under separate control.