Experimental oxygen concentration influences rates of mitochondrial hydrogen peroxide release from cardiac and skeletal muscle preparations.

Mitochondria utilize the majority of oxygen (O) consumed by aerobic organisms as the final electron acceptor for oxidative phosphorylation (OXPHOS) but also to generate reactive oxygen species (mtROS) that participate in cell signaling, physiological hormesis, and disease pathogenesis. Simultaneous monitoring of mtROS production and oxygen consumption (o) from tissue mitochondrial preparations is an attractive investigative approach, but it introduces dynamic changes in media O concentration ([O]) that can confound experimental results and interpretation. We utilized high-resolution fluorespirometry to evaluate o and hydrogen peroxide release (ho) from isolated mitochondria (Mt), permeabilized fibers (Pf), and tissue homogenates (Hm) prepared from murine heart and skeletal muscle across a range of experimental [O]s typically encountered during respirometry protocols (400-50 µM).