Fig. 1.

Generalized models differentiating between actual and apparent rates related to H₂O₂ metabolism in mitochondria. (A) The general model and B–D illustrate the specific conditions used in the experiments of this study. The dashed arrow indicates the direction of net H₂O₂ flux between the medium (extramitochondrial space) and the matrix. (B) Experiments in Series 1 where the H₂O₂ efflux is measured via the H₂O₂ consuming horseradish peroxidase linked assay. (C) Conditions for Series 1 and 2 experiments where the disappearance of exogenously added H₂O₂ is monitored by an electrochemical sensor. Note, the apparent rate of efflux is shown to illustrate the contribution of H₂O₂ production to the underestimate of apparent H₂O₂ consumption. The discrepancy between actual and apparent rates of disappearance may also be due to partial collapse of the inward directed diffusion gradient rather than true efflux. (D) Experiments from Series 3 where the mitochondrial system is allowed to approach steady-state [H₂O₂] in the medium.