Hydrogen peroxide as an endogenous mediator and exogenous tool in cardiovascular research: issues and considerations

Exogenous H2O2 is widely applied to cardiovascular tissues in order to elicit oxidant-dependent responses relevant to signalling and disease. Lower levels of endogenous H2O2 are essential for normal physiological functioning and signalling, whereas higher levels are associated with disease. Within diseased tissues, concentrations in excess of 100 μM have been measured, though 1–15 μM appears to be the upper limit of the healthy physiological range. Analysing the kinetic constants and abundance of peroxidases suggests that they may, on occasion, encounter tissue H2O2 concentrations as high as 1 mM. Extracellular application of 0.01–1 mM peroxide appears to be directly relevant to biology and broadly mimics the release of H2O2 endogenously by growth factors and other effectors. However, the intracellular H2O2 may only ever reach 1–15% of the applied exogenous concentration.