Gill filament permeabilization: A novel approach to assess mitochondrial function in sheepshead minnows (Cyprinodon variegatus) following anthraquinone exposure

Anthracene is a highly toxic polycyclic aromatic hydrocarbon (PAH), and its toxicity is increased 8-fold after compounding exposure to UV radiation. Exposure to either the parent or photo-modified compound has been shown to cause increases in reactive oxygen species (ROS) production and lipid peroxidation. Since the majority of ROS production occurs within mitochondria, we investigated simultaneous mitochondrial respiration and ROS production in the gills of sheepshead minnows (Cyprinodon variegatus) acutely (48 h) exposed to anthraquinone (40 μg l^-1). Anthraquinone exposure caused a 25% increase in oxidative phosphorylation with electrons donated to Complex I (OXPHOS_CI) and a 33% increase in Leak respiration with oligomycin (Leak-Omy_CI). ROS production was slightly increased (33.3%) in Leak state with oligomyocin respiring on Complex I substrates (Leak-Omy_CI) after anthraquinone exposure, but this value remained unchanged in all other respiratory states. When ROS production was normalized to mitochondrial oxygen consumption, we found that ROS production was decreased in all respiratory states, but most noticeably in the Leak state. We speculate that differences in the antioxidant defense system may have played a role in decreased ROS production. Overall, in this paper we present a novel technique to measure mitochondrial function in the gill filaments of teleost fish exposed to xenobiotic molecules, and we show anthraquinone exposure alters aspects of oxidative phosphorylation and ROS production.