Related Experiment Video
Updated: Sep 27, 2026
Protocol for Acute and Chronic Ecotoxicity Testing of the Turquoise Killifish Nothobranchius furzeri
Published on: April 24, 2018
Biochemical characterization of microcystin toxicity in rainbow trout (Oncorhynchus mykiss)
1Institute of Toxicology, Federal Institute of Technology, Schwerzenbach, Switzerland.
Abstract:
The kinetics and biochemical effects of microcystins in rainbow trout were studied with freeze-dried toxic cells of Microcystis aeruginosa, strain PCC 7806. Following in vivo exposure the changes in liver histology were observed over a 72 hr period and the absorption of microcystins from the gastrointestinal tract into the blood and liver, as well as the inhibition of hepatic protein phosphatase 1 and 2A activities, were recorded using the protein phosphatase inhibition assay. The interaction between microcystins and trout liver phosphatases was further tested in vitro using the protein phosphatase inhibition assay. The in vivo experiments demonstrated a high organotropy of microcystins for the liver, where rapid and total inhibition of protein phosphatase 1 and 2A activity was observed. Maximal inhibition of phosphatases was observed 3 hr after gavage. At that time-point, approximately 63% of the toxin present in the liver was refractive to detection via the phosphatase inhibition assay and therefore most likely covalently bound to cellular proteins. The inhibition of hepatic protein phosphatases 1 and 2A proved to be transient only, as a progressive increase in phosphatase activity was observed beginning 12 hr after gavage of the fish, reaching approximately 50% of the control activity at 72 hr. In contrast, liver damage continued to progress despite this renewed protein phosphatase activity.
Insights
Microcystins rapidly inhibit liver phosphatases in rainbow trout, with most toxin covalently bound. However, phosphatase activity recovers over 72 hours, though liver damage persists, indicating complex toxic effects.
Area of Science:
- Environmental Toxicology
- Biochemistry
- Aquatic Toxicology
Background:
- Microcystins are potent hepatotoxins produced by cyanobacteria.
- Rainbow trout are susceptible to microcystin poisoning, impacting aquatic ecosystems.
- Understanding microcystin kinetics and biochemical effects is crucial for risk assessment.
Purpose of the Study:
- To investigate the kinetics and biochemical effects of microcystins in rainbow trout.
- To determine the organ distribution and target enzymes of microcystins in vivo.
- To assess the reversibility of microcystin-induced enzyme inhibition and its relation to liver damage.
Main Methods:
- Exposure of rainbow trout to toxic Microcystis aeruginosa cells.
- Monitoring of liver histology over 72 hours post-exposure.
- Quantification of microcystin absorption and distribution using the protein phosphatase inhibition assay.
- In vitro testing of microcystin interaction with trout liver phosphatases.
Main Results:
- Microcystins exhibited high liver organotropy in trout.
- Complete inhibition of hepatic protein phosphatase 1 and 2A activity occurred within 3 hours.
- Approximately 63% of liver-bound microcystins were covalently bound.
- Phosphatase activity recovered to 50% of control levels by 72 hours, but liver damage progressed.
Conclusions:
- Microcystins cause rapid, transient inhibition of key hepatic phosphatases in rainbow trout.
- Covalent binding of microcystins contributes to their toxicity.
- Progressive liver damage occurs despite partial recovery of phosphatase activity, highlighting complex toxicological mechanisms.
