Effect of Nutrient Availability on Glucose Metabolism
To investigate the potential relationship with glucose metabolism, analyses of extracellular metabolites (glucose, lactate, O2, CO2) in the conditioned media obtained from the final exchange cycle of the culture period were conducted. Glucose consumption and lactate production (Table 1) followed similar trends to the tissue formation results, with maximal consumption/production occurring under intermediate media volumes (Table 1). Under low to intermediate media volumes (1 – 4 mL) metabolism was primarily anaerobic as indicated by the high lactate-on-glucose yield (YL/G) and relatively low magnitude of O2 consumption and CO2 production (Table 1). However, larger media volumes (> 4 mL) appeared to alter metabolism from primarily anaerobic to mixed aerobic-anaerobic with a steep decline in YL/G as well as observed increases in O2/CO2consumption/production (Table 1). Lastly, extracellular pH did not follow a similar trend, but rather experienced monotonic increases (alkaline) with increasing media volume (Table 1).