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.