The effects of exposure to heavy metal ions on cytochrome b₅ and components of the mixed-function oxidases from the digestive gland microsomes of the mollusc Monodonta turbinata

LT₅₀ values obtained for Monodonta turbinata exposed to heavy metal ions were as follows: 25.2 days after exposure to final concentration of 1.0 ppm Cd⁺²; 21.2 days for 0.1 ppm Hg⁺²; 25.2 for 0.5 ppm Cr⁺³ and 16.8 days for 0.5 ppm Cr⁺⁶, compared to 32.8 days for the control. The final concentrations of metal ions in the mollusc tissue increased by 20 times in the Hg⁺², and by 10 times in the Cd⁺² treated Monodonta, compared to the untreated control. The normal contents of cytochromes b₅ and P450 in Monodonta turbinata digestive gland microsomes were 195 ± 51 and 58 ± 20 nmol/mg protein, respectively. NADPH-cytochrome c reductase activity was 5.9 ± 3.0 nmol/min/mg protein. Exposure to all heavy metal ions had a destructive effect on the two hemoproteins, especially on cytochrome P450, and a pronounced impact on NADPH-cytochrome c activity which was reduced to about 50% in the treated mollusc. No alarming concentrations of metal ions could be detected in Monodonta turbinata collected from different sites along Israel Mediterranean coast.