Fig. 4From: Fast exchange fluxes around the pyruvate node: a leaky cell model to explain the gain and loss of unlabelled and labelled metabolites in a tracer experimentConcentration profiles of extracellular metabolites pyruvate, lactate and glucose from culture medium of HEK293 cells. Unlabelled and fully labelled fractions are shown as white and grey bars. Pyruvate, lactate and glucose concentrations were quantified using ions 142, 115 and 314, respectively. Pyruvate in EM was slightly less enriched than in FM despite glucose in EM was more labelled than in FM (71.7 vs. 46.9 %). Pyruvate is proximal to glucose compared to lactate and thus was more enriched. Pyruvate enrichment, however, correlated strongly with lactate’sBack to article page