Pericellular P_O2 and O₂ consumption in monolayer cell cultures

The current study was based on the uncertainty as to how well monolayer cell cultures growing in customary polystyrene dishes are supplied with O₂. For dishes maintained in an air-5% CO₂ atmosphere at 37°C, microelectrode measurements revealed that the pericellular steady-state P_O2 was 78 mm Hg in confluent bovine endothelial, 110 mm Hg in rat renal mesangial, and 0 (<0.2) mm Hg in renal (LLC-PK₁ and LLC-MK₂) or hepatic (HepG2, Hep3B) epithelial cell cultures. These measured P_O2 values were in good agreement with those calculated from Fick's law of gas diffusion, applied for the present culture conditions (one-dimensional O₂ diffusion, 0.52 cm medium height), the individual cell layer density and the tissue-specific rate of O₂ utilization. Our results provide reasons to speculate that conventional monolayer cultures are often hypoxic when incubated in an air-5% CO₂ atmosphere. Diffusion-limitations of cellular O₂ availability are to be taken into consideration when tissue cultures are used to study P_O2-dependent processes.