Oxidative Status of Planarians is Differently Affected by PAHs: 3-5 Benzene Ring Compounds

Abstract

Planarians are promising model animals and are increasing in importance for ecotoxicological studies. However, there is scarce to no information for many contaminants, such as polycyclic aromatic hydrocarbons (PAHs), regarding their specific toxicity towards planarians. We aimed to uncover how vital physiological functions, such as, neurophysiology, detoxification and oxidative stress status, and cellular energy allocation are affected on the freshwater planarian Girardia tigrina by low and high molecular weight PAHs – phenanthrene, pyrene and benzo[a]pyrene (B[a]P). Phenanthrene affected planarian antioxidant defences and detoxification, increasing glutathione levels and activity of glutathione-S-transferase (GST), the latter in a dose-dependent way (from 75 to 300 µg L^-1). Phenanthrene also decreased carbohydrates in planarians exposed to 150 and 300 µg L^-1. Pyrene caused higher oxygen consumption and decreased energy budget in planarians exposed to 75 and 150 µg L^-1. B[a]P exposure decreased G. tigrina GST activity in a dose-dependent way. Lower lipid peroxidation levels were measured in planarians exposed to 2.5 and 75 µg L^-1 of pyrene and at 37.5, 75 and 150 µg L^-1 of B[a]P. The present data indicate that each of these PAHs seems to elicit distinct biochemical responses in planarians, possibly pointing to different biochemical interactions and/or metabolisation of each compound.

Keywords: Epibenthic freshwater planarians, polycyclic aromatic hydrocarbons, oxidative stress status, energy budget, lipid peroxidation