Glucose Metabolism
Extracellular metabolites (glucose, lactate, O2, CO2) and pH were determined in the conditioned media obtained from the last exchange cycle (after 48 hours) of the 4-week culture period. Glucose and lactate in the media were detected using enzymatic assays (Lockridge et al. , 1972; Blake & McLean, 1989) and expressed in terms of consumption or production. Changes in metabolism were then assessed by determining the yield of lactate-on-glucose (YL/G; with 2 representing 100% anaerobic metabolism) as well as relative changes in O2consumption (qO2) and CO2 production (qCO2), estimated from pO2 and pCO2 levels (Radiometer ABL825). All results were normalized to DNA content.