Biochemical evaluation of naphthalene intoxication in the tropical acrid blood clam Anadara granosa

Abstract

Exposure of the tropical arcid blood clam Anadara granosa L., collected from Bombay waters in 1986, to sublethal concentrations of naphthalene (Nap) (5, 10 and 15μg Nap ml-1), induced various changes in vital biochemical systems. The condition index (CI) remained largely within the control range, although tissue water content after 96h exposure increased significantly (p<0.001). Glycogen levels appreciably decreased, both in muscles (p<0.001) and digestive glands (p<0.01). AMP activity remained unaltered irrespective of the ambient Nap concentration. ADP levels decreased by more than 20% and ATP levels also decreased significantly (p≪0.001) by more than 60% with increases in ambient Nap levels from 5 to 15 μg ml-1. Lysosomal marker enzymes-arylsulphatase and acid phosphatase-showed various changes. Levels of the former were 10 to 17 times higher than the latter. Total and free arylsulphatase activity in hepatic cells decreased on exposure of clams to 5 and 10μg Nap ml-1, but not significantly. However, it was significantly inhibited (p<0.001) towards the upper limits of exposure concentration. The same was also true of acid phosphatase activity. Nicotinamide adenine dinucleotide (NADH2) oxidation of lipochrome showed a dramatic decrease in activity in the range of 37 to 88% over controls with increasing Nap from 5 to 15 μg ml-1. Fatty acids also exhibited significant changes in composition with a decrease in polyunsaturated acids and an increase in certain saturated fatty acids. Protein and carbohydrate levels increased significantly (p<0.001) towards upper limits of exposure concentration. Pyruvic acid levels increased significantly by 2 to 6 times over controls on exposure to 5 to 15 μg Nap ml-1. Explanation of these changes is attempted in terms of the glycolysis pathway involving pyruvic acid oxidation and oxidative phosphorylation in the electron transport system.