Changes of cholinesterase activity, histology and proteome of puntius javanicus liver upon exposure to copper

The present study was carried out to investigate the effect of copper sulfate (CUSO₄) exposure on cholinesterase (ChE) activity, histology, and proteome of Punt ius javanicus liver. Acute toxicity test to obtain lethal concentration (LC) values (LC₅₀o and LC10) of CUSO₄ was initially done by exposing eight groups of fish for 96 hours with 2.0, 4.0, 6.0, 8.0, 10, 13, 15 and 20 mg/L of CUSO₄, respectively. Based on Finney method (Probit analysis) of calculation, LC₅o and LC10 of CUSO₄ were determined as at 10.30 mg/L and 6.11 mg/L, respectively. Sublethal CUSO₄ concentrations of 0, 0.1,0.3, 0.5, 1.0 and 5.0 mg/L (Lower than LC10 value i.e. with 100% fish survival) were used to treat six groups of P. javanicus fish including a control for 96 hours. The liver of each treated and control fish was subjected to cholinesterase activity test, histology, and proteomic studies. For ChE activity study, an optimal assay condition of purified ChE was determined as at the pH 7.5 and at the temperature in the range of 25 to 35°C in 0.1M Sodium Phosphate buffer. As compared to other synthetic substrate, butyrylthiocholine iodide (BTCi) was selected as ChE specific substrate with the highest maximal activity (Vmax), lowest biomolecular constant (Km) and the highest catalytic efficiency ratio at the value of 53.49 (50.12 to 56.87)µmol/min/mg, 0.23 (0.16 to 0.31) mM, and 232.57, respectively. Storage condition showed that ChE need to be preserved in refrigerated condition. Metal ion in-vitro test showed that Cu, chromium and mercury had the capability to lowering the activity of ChE more than 50%. The combination of pairwise metal ion enhanced the inhibitory effect of more than 60%. Half inhibitory effect (IC₅o) of Cu ion towards the ChE In vitro was found as at 0.0948 (0.06797 to 0.1628) mg/L. In vivo effect showed that at 0.1 mg/L of CUSO₄, the activity of ChE was increased significantly (p