The biological activity of the organic UV filter ethylhexyl methoxycinnamate in rainbow trout (Oncorhynchus mykiss)

Abstract

UV filters are able to enter the aquatic environment and negatively affect non-target organisms. The aim of this study was to evaluate subchronic exposure to ethylhexyl methoxycinnamate (EHMC) in rainbow trout. The tested EHMC concentrations of 6.9 (low), 96.0 (medium) and 395.6 μg/kg (high) were used. The lowest concentration was based on environmentally relevant concentrations. The higher concentrations were chosen as a multiple of the lowest one to determine the dose-response relationship. EHMC was incorporated into feed pellets. The experiment was conducted for six weeks in a semi-static system. Haematological, biochemical and oxidative stress indices were determined at the end of the experiment and supplemented by histological examination. Significant changes were proven at medium and high concentrations of EHMC. Specifically, increases of glucose, lactate and decrease of albumin and total protein in plasma indicate a stress ethology. Moreover, a decrease of plasma cholesterol, triacylglycerols and ammonia were observed even in the experimental group exposed to the lowest concentration of EHMC, perceived as an environmentally relevant concentration. The ferric reducing ability of plasma was decreased in all tested concentrations. Exposure to the highest concentration of EHMC resulted in a decrease in leukocyte counts. Increased activity of glutathione peroxidase in liver was recorded for the medium and the highest concentration of EHMC. The level of the thiobarbituric acid reactive substances in kidney was elevated for the highest concentration. Decrease of the activity of glutathione-S-transferase in gills for medium concentration of EHMC was registered. Histopathological examination revealed massive destruction of hepatic parenchyma at the highest concentration of EHMC. All these results support the finding of a stress load on the fish organism. In summary, although subchronic exposure to EHMC had no effect on behaviour, mortality or feed intake, this exposure resulted in the alteration of saccharide, lipid and protein metabolism and weakened antioxidant capacity.

Keywords: Aquatic ecosystem; EHMC; Fish; Haematological and biochemical indices; Histopathology; Oxidative stress.