Recently experimentally exposed common carp took
Recently, experimentally-exposed common carp took up CLO from water and maintained a consistent concentration in the liver and blood plasma (Corcoran et al., 2014). Clotrimazole may influence other aquatic organisms. Survival and development of marine shrimp larvae (Palaemon serratus) were affected at 2.78 μg L−1 (González-Ortegón et al., 2015), and morphological changes were observed at 3.16 μg L−1 (González-Ortegón et al., 2013).
Because CLO belongs to the antifungal group of medications containing an imidazole ring, it can affect the activity of cytochrome P450 (CYP450) (Verras and Ortiz de Montellano, 2006). Antifungals act through the inhibition of CYP450-dependent 14α-demethylase, which is critical to ergosterol biosynthesis (Rupp et al., 2005). Despite anatomical differences, many physiological and biochemical processes in fish are remarkably similar to those in humans. For example, the fish CYP450 enzyme system shares 50% identity with the corresponding mammalian system (Huggett et al., 2003). The cysteine protease form an extremely important metabolic system because of their involvement in regulating the titres of endogenous compounds such as hormones, fatty acids and steroids. Thus, the physiological processes in fish may be affected by the presence of CLO. Clotrimazole has been shown to be a potent modulator of many mammalian and fish CYP450-mediated reactions, including sterol 14α-demethylation [CYP51; (Ford, 2004)], ethoxyresorufin-O-deethylation [CYP1A; (Burkina et al., 2013)], 7-benzyloxy-4-trifluoro-methylcoumarin (BFC) debenzylation [CYP3A; (Burkina et al., 2013)], and others (Ronis et al., 1998, Zhang et al., 2002, Hinfray et al., 2006, Wassmur et al., 2013). In addition, it modulates cellular Ca2+ homeostasis in mammals (Snajdrova et al., 1998, Klokouzas et al., 2002) and steroidogenesis in aquatic organisms (Hinfray et al., 2011, Baudiffier et al., 2012, Baudiffier et al., 2013).
In general, fungicides may induce cellular damage in aquatic organisms e.g. [(Li et al., 2010a, Li et al., 2010b, Li et al., 2010c, Toni et al., 2011)]. Among cellular toxicity mechanisms, oxidative stress, defined as an imbalance between pro-oxidant and antioxidant cellular forces, causes oxidative damage to tissues (Ashtiani et al., 2011). This occurs mainly in the endoplasmic reticulum of exposed cells where CYP450 activities may generate reactive oxygen species (ROSs) as by-products of detoxification processes. Liver and gill tissues are considered to be the most susceptible in fish, and both enzymatic (superoxide dismutase, catalase and peroxidases) and non-enzymatic (e.g., vitamins and glutathione) antioxidants are used to manage this. The alterations of these enzymes during antioxidant defence are used as biomarkers in response to oxidative stress (van der Oost et al., 2003). So far, little information has been available on the oxidative effects of CLO in fish. Sub-chronic toxicity tests can provide useful information for understanding possible ecotoxicological effects of human pharmaceuticals on aquatic organisms.
The aim of this study was to assess the sub-chronic effects of CLO at two environmentally relevant CLO concentrations and one sub-lethal concentration on juvenile rainbow trout (Oncorhynchus mykiss). Specifically, it aimed to 1) investigate the impact of CLO exposure on the haematological and biochemical profiles of blood plasma and the histology of the kidney, liver, gill and gonads; 2) measure the enzymatic activities involved in detoxification and levels of lipid peroxidation in the liver, gills and brain; 3) examine tissue-specific CLO concentrations followed by a depuration period of 7 or 13 days; and 4) determine CLO concentrations in faeces.
Materials and methods
Discussion Verifying actual exposure under laboratory conditions is crucial for compounds with high partition coefficients (Kow) such as CLO (Peschka et al., 2007, González-Ortegón et al., 2013, Corcoran et al., 2014). The significantly different adsorptions of CLO between aquaria containing fish and those without fish suggests that under experimental conditions, CLO may have been partly adsorbed by aquaria surfaces (insignificant portions), and it was probably first taken up by fish and then absorbed by organic matter.