Toxicity of Microcystis aeruginosa peptide toxin to yearling rainbow trout (Oncorhynchus mykiss)

Abstract

The effects of the blue-green algae (cyanobacterial) toxin microcystin-LR on yearling rainbow trout were studied in a series of intraperitoneal injection tests, gavage trials and exposures to waterborne algae. Concentrations of the microcystin-producing algae Microcystis aeruginosa known to occur during algae blooms (8-16 mg freeze-dried algae/L, i.e. approximately 1-2 × 1011 cells/L) were shown to be non-toxic to trout when present in aquarium water. On the other hand, trout died within 96 h when gavaged with an amount of algae equivalent to that which passed through the gills within 18 h in the aqueous exposure tests (1440 mg freeze-dried algae/kg body weight, i.e. 6600/.tg microcystin/kg body weight). Oral uptake of approximately one tenth of this dose (110 mg freeze-dried algae/kg body weight, i.e. 550/lg microcystin/kg body weight) proved to be non-toxic in single gavaging studies, but toxic within 96 h when orally administered 8 times at 12-h intervals. This study shows that the main uptake route of microcystin in trout is the gastrointestinal tract and that toxicity is manifested as massive hepatic necrosis. These results indicate that massive fish deaths reported at cyanobacterial bloom sites can be explained by the ingestion of toxic blue-green algae.

Quantitatively evaluating detoxification of the hepatotoxic microcystin-LR through the glutathione (GSH) pathway in SD rats

“…For instance, the median lethal dose (LD 50 ) of MC-LR via intraperitoneal (i.p.) injection is approximately 50-60 μg/kg body weight (BW) in mice (Botes et al 1984;Carmichael et al 1988) and 72 and 122 μg/kg BW for fasted and fed rats (Miura et al 1991), respectively, but increases to 300-550 μg/kg BW in common carp (Cyprinus carpio) (Råbergh et al 1991), to 400-500 μg/ kg BW in rainbow trout (Oncorhynchus mykiss) (Tencalla et al 1994;Kotak et al 1996) and even to 1500 μg/kg BW in perch (Pera fluviatilis) (Ibelings et al 2005). Nevertheless, so far, there is no literature on simultaneous quantification of MC-LR and its two main metabolites and the GSH detoxification dynamics of MCs in mammals, and the role of GSH in the detoxification of MCs in mammals remains largely unknown.…”

Hepatic Histopathological Characteristics and Antioxidant Response of Phytoplanktivorous Silver Carp Intraperitoneally Injected with Extracted Microcystins

“…In rainbow trout, all fish in 1 000 μg MC-LR/kg BW dose group (i.p.) died within 25 h but no death was reported at the dose of 400 μg/kg BW or less, suggesting that the 24 h LD 50 ranges 400-1 000 μg/kg BW [22] , and the mortality of rainbow trout is 100% within 24 h after injection of 550 μg MC-LR/kg BW [23] . It was reported that the LD 50 of MC-LR in Carassius auratus is 380 μg MC-LR/kg BW [24] .…”

Response and recovery of hybrid sturgeon from subchronic oral administration of cyanobacteria

“…In fish, cyanobacterial toxins may ingestion via different route: direct feeding on toxic cyanobacterial cells, uptaking of dissolved toxins via the gill epithelium or exposure via the foodweb (Tencalla et al, 1994;Bury et al, 1998;Ibelings and Chorus, 2007). However, the harmful effects of MCs on fishes were mainly limited to acute toxic exposure routes and they were based on either oral gavaging, or intraperitoneal injection, or administration via the dorsal aorta of the toxins (Carbis et al, 1996;Bury et al, 1997;Li et al, 2005), which cannot reflect the uptake route under natural environments.…”