Abstract
Low magnetic fields (LMFs) of less than 1 × 10(-3) Tesla (T) affect numerous biological processes, including plant growth and bird migration. At a cellular level, LMFs influence intracellular Ca(2+) concentrations and generation of mitochondrial reactive oxygen species (mROS). However, the mechanisms that account for these effects are controversial. Here, by applying a static LMF, ranging from ∼2.7 × 10(-4) to ∼1.9 × 10(-3) T, to mitochondria isolated from adult rat hearts, a bell-shaped increase in State 3 respiration (S3R) was observed, up to 40 %. A similar LMF-induced increase in S3R was also observed in mitochondria from rat hearts subjected to ischemia-reperfusion injury. The LMF-mediated bell-shaped response was also observed in enzymes activity involved in oxidative phosphorylation (OXPHOS), including Complexes II, III, and V, and citrate synthase. By contrast, similar LMF caused little change in the enzymatic activity of Complex I. Interestingly, mROS generation responded to LMF with an inverted bell-shaped decrease. We propose a radical pair mechanism of magnetoreception in cytochromes, catalytic reactions, and iron-sulfur clusters within the OXPHOS enzymes to explain how an LMF can increase the likelihood of electron spin transitions from the singlet to triplet state and reverse it as the MF strength further increases, resulting in a bell-shaped response. Our results indicate that a narrow range of LMF can enhance mitochondrial bioenergetics and decrease mROS, through the radical pair mechanism of magnetoreception. These basic findings in isolated cardiac mitochondria may encourage future studies that apply quantum mechanics to explore the mitochondrial electron transfer system.