Accumulation and biochemical effects of microcystin-LR on the Patagonian pejerrey (Odontesthes hatcheri) fed with the toxic cyanobacteria Microcystis aeruginosa

Abstract

We studied accumulation and biochemical effects of microcystin-LR (MCLR) in Odontesthes hatcheri after dietary administration of the cyanobacteria Microcystis aeruginosa (1.3 μg MCLR/g body mass, incorporated in standard fish food). After 12 h, MCLR content in liver did not differ between fish fed with crushed or intact cells, demonstrating O. hatcheri's capacity to digest cyanobacteria and absorb MCLR. In the second experiment, fish received toxic cells, non-toxic cells, or control food; MCLR accumulation was monitored for 48 h. Protein phosphatase 1 (PP1), catalase (CAT), glutathione-S-transferase (GST) activities, and lipid peroxidation (as MDA) were measured in liver and intestine. Methanol-extractable MCLR was determined by PP1 inhibition assay (PPIA); extractable and protein-bound MCLR were measured by Lemieux oxidation-gas chromatography/mass spectrometry (GC/MS). MCLR accumulated rapidly up to 22.9 and 9.4 μg MCLR/g in intestine and liver, respectively, followed by a decreasing tendency. Protein-bound MCLR represented 66 to ca. 100 % of total MCLR in both tissues. PP1 activity remained unchanged in intestine but was increased in liver of MCLR treated fish.CAT and GST activities and MDA content were significantly increased by MCLR only in liver. We conclude that O. hatcheri is able to digest cyanobacteria, accumulating MCLR mostly bound to proteins. Our data suggest that this freshwater fish can be adversely affected by cyanobacterial blooms. However, the rapid decrease of the detectable MCLR in both tissues could imply that sublethal toxin accumulation is rapidly reversed.

Effects of dietary protein levels on the disease resistance, immune function and physical barrier function in the gill of grass carp ( Ctenopharyngodon idella ) after challenged with Flavobacterium columnare

“…In the present study, compared with low or high levels of protein, at optimal levels of dietary protein, the contents of ROS, MDA and PC decreased in the gills of grass carp, indicating that an optimal level of dietary protein protected fish from oxidative damage to the gill. To our knowledge, oxidative damage is closely associated with non-enzymatic antioxidants such as GSH and antioxidant enzymes such as CAT and GPx in fish [77,78]. In the present study, compared with low or high levels of protein, at optimal dietary protein levels, the activities of CAT, GPx, GST and GR and the content of GSH were increased in the gills of grass carp, suggesting that at an optimal level of dietary protein the antioxidant capacity of fish gill improved.…”

Cellular transport of microcystin-LR in rainbow trout (Oncorhynchus mykiss) across the intestinal wall: Possible involvement of multidrug resistance-associated proteins

“…This transport has been studied in mammals, in cell lines, and in fish tissues (Eriksson et al, 1990;Runnegar et al, 1995;Fischer et al, 2005;Boaru et al, 2006;Meier-Abt et al, 2007;Lu et al, 2008). In aquatic animals, laboratory and field studies demonstrate that tissue accumulation of MC is followed by metabolization and elimination, limiting MC accumulation and transfer along the food chain (Williams et al, 1997a, b;Amorim and Vasconcelos, 1999;Soares et al, 2004;Ibelings and Chorus, 2007;Bieczynski et al, 2013). However, the mechanistic events implied in MCLR detoxification and elimination have not been elucidated so far.…”

“…For preparation of everted sacs, pieces of intestine were put in a Petri dish with ice-cold saline and slid onto a crochet needle to expose the mucosal surface. For non-everted sacs, pieces of intestine were cut, placed in (Williams et al, 1997a;Bieczynski et al, 2013), in which ca. 30% of the applied dose has been detected in liver and intestine tissue, respectively.…”

A sensitive method for the determination of total microcystins in water and sediment samples by liquid chromatography with fluorescence detection

“…9 Bieczynski et al found that protein-bound MC-LR (L ¼ leucine, R ¼ arginine) represented 66-100% of total MC-LR in the intestine and liver. 10 Our previous studies also revealed that MCs can be strongly adsorbed by sediment, but only be partly recovered by solvent extraction.…”