An Assay for the Rate of Removal of Extracellular Hydrogen Peroxide by Cells.

Cells have a wide range of capacities to remove extracellular hydrogen peroxide. At higher concentrations of extracellular HO (micromolar) the rate of removal can be approximated by a rate equation that is first-order in the concentration of HO and cell density. Here we present a method to determine the observed rate constant for the removal of extracellular HO on a per cell basis. In the cells examined, when exposed to 20 μM HO, these rate constants () range from 0.46 × 10 s cell L for Mia PaCa-2 cells (human pancreatic carcinoma) to 10.4 × 10 s cell L for U937 cells (human histiocytic lymphoma). For the relatively small red blood cell = 2.9 × 10 s cell L. These rate constants, , can be used to compare the capacity of cells to remove higher levels of extracellular HO, as often presented in cell culture experiments. They also provide a means to estimate the rate of removal of extracellular HO, rate = - [HO] (cells L), and the half-life of a bolus of HO. This information is essential to optimize experimental design and interpret data from experiments that expose cells to extracellular HO.