Rapid Method for Assessing Oxygen Consumption Rate of Cells from Transient-state Measurements of Pericellular Dissolved Oxygen Concentration

Abstract

Recently we described a method for estimating the oxygen consumption rate (OCR) of cells in static culture from equilibrium measurements of dissolved oxygen concentration (dO2), using an oxygen-sensing microplate and the steady-state solution to Fick's Law (Guarino et al. 2004). Here we describe a complementary method for estimating OCR from the transient-state rate of change of measured dO2. Although the system is open to the atmosphere and subject to a significant lag in sensor response, the rate of change of the measured dO2 immediately after seeding correlated directly with both cell number and steady-state OCR. This transient-state method is linear with cell number to a much higher density than is possible with the steady-state method because it derives from measurements made before diffusion limitations can be established. For a given sensor thickness, the same correlation line between the transient and non-diffusion-limited steady-state estimates of OCR was found to apply for various preparations of rat hepatocytes. The correlation slope varied predictably with sensor thickness. Thus, despite the non-idealities of this system, the initial rate measurement offers a rapid method to obtain an estimate of absolute OCR. To demonstrate the utility of this method, we purposefully treated rat hepatocytes in ways expected to change OCR. Cells deprived of oxygen by storage under several centimeters of medium showed decreases in both OCR and viability with time. Likewise, the OCR of hepatocytes exposed to the oxidative phosphorylation inhibitor rotenone decreased, whereas those exposed to the uncoupler dinoseb increased.