Effect of cadmium on some aspects of carbohydrate metabolism in a freshwater catfish Heteropneustes fossilis.

The chronic toxic effects of cadmium (0.26 mg/l) on the carbohydrate metabolism of a teleost fish, Heteropneustes fossilis were examined after 15, 30 and 60 days of exposure. The alterations produced after 15 and 30 days of exposure were similar in nature but were different in fish treated for 60 days. Fish were hyperglycemic and hyperlactacidemic after 15 and 30 days of exposure. The liver and muscle glycogen content was depleted in the first two periods of exposure. In contrast, 60 days of cadmium treatment increased the glycogen content of the two tissues. Liver lactic acid level was elevated after 15 days. Muscle lactic acid content fell significantly after 15 and 60 days of exposure, but it was elevated after 30 days. In general, the activities of lactate dehydrogenase, pyruvate dehydrogenase and succinate dehydrogenase increased in liver, kidney, intestine, ovary, gills and muscles of fish exposed to cadmium for 15 and 30 days. The increase in activities of the three dehydrogenases continued up to 60 days in intestine and ovary. In gills succinate dehydrogenase activity was elevated after 60 days also, but pyruvate dehydrogenase was inhibited. The activities of the three dehydrogenases decreased in liver, kidney and muscles.