Changes in the activities of some digestive enzymes of Channa punctatus, exposed chronically to mercuric chloride.

The effect of a chronic exposure to sublethal concentration of mercuric chloride (0.3 mg/l) on the activities of some enzymes in the digestive system of the teleost fish Channa punctatus was examined after 15 and 30 days of treatment. Glucose-6-phosphatase was significantly inhibited in the intestine and pyloric caeca. No marked alterations were observed in the activities of maltase and lactase except for elevation in maltase activity and inhibition in lactase activity in the intestine and pyloric caeca after 15 days of treatment. Three peptidases (aminotripeptidase, glycylglycine dipeptidase and glycyl-1-leucine dipeptidase) showed decreased activities in all parts of the digestive system. A decrease was also observed in the activity of lipase except for the stomach where inhibition after 15 days was insignificant. The results indicate that the activities of all the enzymes examined are inhibited in intestine and pyloric caeca and digestion of proteins and lipids may be more affected by mercury than the digestion of some carbohydrates.