The effect of the toxicant on the activity of lysosomal hydrolases in organs of the White Sea mussels Mytilus edulis (Linnaeus 1758) was studied in aquatic experiments simulating a crude oil spill in the tidal zone. The mollusks were exposed for 1, 5 and 10 days to three
pollutant concentrations (0.05; 0.25, and 2.50 ml/l). The impact of oil pollution was studied in combination with salinity normal for White Sea surface water (25 ‰) and low (15 ‰), which corresponds to reality during oil spills on the coast and in estuaries. We determined
the activity of six lysosomal enzymes (acid phosphatase, RNase, DNase, β-glucosidase, β-galactosidase, and β-glucuronidase) in the gills and hepatopancreas. Both factors (sea water desalination and oil impact) had a significant effect on the activity of acid hydrolases. The most pronounced lysosomal reaction to oil appeared in the gills under normal salinity at 0.25 ml/l concentration and exposure for 10 days, as evidenced by a several-fold increase in the activity of acid phosphatase, DNase, β-galactosidase, and β-glucuronidase compared to the control. In the hepatopancreas, the same dependence in enzyme activity was noted, but to a lesser extent. Seawater desalination to 15 ‰ in the control caused a slight increase in the activity of DNase, β-galactosidase, and β-glucuronidase in the gills, while the effect for the hepatopancreas was insignificant. The combined effect of desalination and oil pollution somewhat reduced the protective functions of the lysosomal apparatus in mussels organs, which was especially noticeable at high oil concentrations and prolonged exposure of mollusks to experimental conditions. Thus, the results of the study demonstrate active participation of the lysosomal apparatus of the gills and hepatopancreas of mollusks in the adaptive responses to the combined effects of oil pollution and low water salinity.
Compensatory changes in the activity of the enzyme complex of lysosomes are aimed at the utilization, transformation and excretion of oil components from the body, elimination of the structures and macromolecules damaged by the toxicant, as well as maintaining the
vital activity of the organism under adverse conditions.