Cholinesterase activity as potential biomarker in two bivalves

Area of Science:

• Environmental toxicology
• Marine biology
• Biochemistry

Background:

• Cholinesterases (ChE) are crucial enzymes for neurotransmission.
• Bivalves are important indicators of aquatic ecosystem health.
• Pesticide contamination poses a significant threat to aquatic life.

Purpose of the Study:

• To optimize assay conditions for cholinesterases (ChE) in two bivalve species: Mytilus galloprovincialis and Corbicula fluminea.
• To evaluate the sensitivity of bivalve ChEs to common pesticides.
• To assess the suitability of these bivalves as sentinel organisms for pesticide monitoring.

Main Methods:

• Optimization of pH, temperature, and substrate specificity for ChE assays.
• Determination of apparent K(m) values for acetylthiocholine (ASCh) and propionylthiocholine (PrSCh).
• In vitro and in vivo assessment of ChE sensitivity to carbaryl and methylparathion.

Main Results:

• Optimal assay conditions determined: pH 7, 25°C, 2 mM ASCh for M. galloprovincialis; pH 8, 25°C, 5 mM PrSCh for C. fluminea.
• Apparent K(m) values were 30 μM for M. galloprovincialis and 70 μM for C. fluminea.
• Bivalve ChE activity levels were low compared to crustaceans and fishes. Pesticide sensitivity was comparable to fishes but lower than crustaceans.

Conclusions:

• Optimized ChE assays provide a basis for further toxicological studies in these bivalves.
• Mytilus galloprovincialis and Corbicula fluminea exhibit potential as sentinel species for detecting acute pesticide contamination.
• Further research is needed to explore responses to a wider range of contaminants.