Impact of sublethal concentration of mercury on nitrogen metabolism of the freshwater fish, Cyprinus carpio (Linnaeus).

Exposure of the freshwater fish, Cyprinus carpio, td a sublethal concentration of mercury (0.1 mg/l) resulted a progressive decrease in soluble, structural and total proteins in the liver, brain and muscle on days 1 and 15, but their levels significantly regained on day 30. Corresponding to the fluctuations in proteins, an elevation was observed in the levels of free amino acids and in the activities of protease, amino transferases (AIAT & AAT) and GDH. Ammonia level in the liver and blood increased progressively on days 1 and 15 and regressed on day 30; the urea level, however, increased over time of exposure. In brain and muscle though ammonia level increased (day 1 > 15 > 30) with a corresponding decrease in urea level (day 1 < 15 < 30), these changes were insignificant. All these observations revealed an initial high proteolysis in the tissues of the fish on sublethal mercury intoxication with a recovery on long-term exposure to a period of 30 days. Among,the tissues the degree of proteolysis was in the order : liver > muscle > brain.