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 H(2)O(2) (micromolar) the rate of removal can be approximated by a rate equation that is first-order in the concentration of H(2)O(2) and cell density. Here we present a method to determine the observed rate constant for the removal of extracellular H(2)O(2) on a per cell basis. In the cells examined, when exposed to 20 μM H(2)O(2), these rate constants (k(cell)) range from 0.46×10(−12) s(−1) cell(−1) L for Mia-PaCa-2 cells (human pancreatic carcinoma) to 10.4×10(−12) s(−1) cell(−1) L for U937 cells (human histiocytic lymphoma). For the relatively small red blood cell k(cell)=2.9×10(−12) s(−1) cell(−1) L. These rate constants, k(cell), can be used to compare the capacity of cells to remove higher levels of extracellular H(2)O(2), as often presented in cell culture experiments. They also provide a means to estimate the rate of removal of extracellular H(2)O(2), rate=−k(cell) [H(2)O(2)] (cells L(−1)), and the half-life of a bolus of H(2)O(2). This information is essential to optimize experimental design and interpret data from experiments that expose cells to extracellular H(2)O(2).