UTILIZATION OF 14C-LABELLED GLUCOSE BY HUMAN CELLS (STRAIN HLM) IN TISSUE CULTURE

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Abstract
A C14-tracer technique was developed and used to investigate the utilization of C from C14-labelled glucose in proliferat-ing cell cultures of the premanent strain HLM, derived from human fetal liver. With uniformly labelled glucose ([U-C14]-glucose), 9-26%of the C14 activity metabolized was found in CO2 and 5-18% was incorporated into the cell constituents (ie acidsoluble compounds, lipids, nucleic acids and proteins), in cultures analysed at different times and in different media. The incorporation of C from NaHC14O3 was negligible in these cells. The addition of insulin (1 unit/ml) to the culture medium produced a marked stimulation of glycolysis. HLM cells cultivated for sufficient time in the absence of insulin grew more slowly than replicate cultures kept in medium containing insulin. The presence of insulin did not significantly alter the distribution of glucose C amongst cell constituents and CO2. [1-C14] Glucose produced higher activity in CO2 than did [6-C14] glucose, indicating some metabolism via the pentose-shunt pathway. From the differences observed in the amounts of activity located in total acid produced or in CO2, by using [1-C14]-glucose respectively, and on the basis of certain assumptions, it was estimated that 10-20% of the glucose utilized was metabolized through the shunt.