Restoration of Muscle Function Following Pyrene Exposure and Depuration in Rana pipiens

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a major group of diverse environmental organic pollutants formed mostly by incomplete combustion of fossil fuels. Previous studies in our laboratory revealed that in-water exposure of the leopard frog, Rana pipiens, to the PAHs naphthalene and pyrene caused a significant reduction in muscle performance (e.g., contractile force). The purpose of the present study was to investigate whether the adverse effects of in-water pyrene exposure could be reversed during depuration experiments. Frogs were exposed to a pyrene-saturated water environment for 7 days. Depuration experiments involved transferring pyrene-exposed frogs to clean water environments for periods of 4 to 25 days following the pyrene exposure. Swimming performance, muscle contractile force, mitochondrial O2 consumption and membrane potential were analyzed in control frogs and in frogs immediately following pyrene-exposure and at 4, 7, 13, and 25 days post-exposure. Pyrene significantly (P≤0.05) reduced swimming performance to 22±6% of control. Following 25 days of depuration, swimming performance was 98±8% of control. Mitochondrial O2 consumption was 78±4% of control immediately following exposure, and 77±2%, 85±2%, 94±2%, and 97±7% of control at 4, 7, 13, and 25 days post-exposure, respectively. Effective depuration was also evident for muscle contractile force and mitochondrial membrane potential. These data suggest that the adverse effects of pyrene exposure on frog muscle function could be reversed providing that the animals are transferred to clean water environments for extended periods of time. Funding support provided by a Bradley University Biology Department Bjorkland Research grant and a Tri-Beta Research grant to AFB.