IMPACT OF SUBLETHAL CONCENTRATION OF MERCURY ON NITROGEN METABOLISM OF THE FRESH-WATER FISH, CYPRINUS-CARPIO (LINNAEUS)

Exposure of the freshwater fish, Cyprinus carpio, td a sublethal conce ntration of mercury (0.1 mg/l) resulted a progressive decrease in solu ble, structural and total proteins in the liver, brain and muscle on d ays 1 and 15, but their levels significantly regained on day 30. Corre sponding to the fluctuations in proteins, an elevation was observed in the levels of free amino acids and in the activities of protease, ami no transferases (AIAT & AAT) and GDH. Ammonia level in the liver and b lood increased progressively on days 1 and 15 and regressed on day 30; the urea level, however, increased over time of exposure. In brain an d muscle though ammonia level increased (day 1 > 15 > 30) with a corre sponding decrease in urea level (day 1 < 15 < 30), these changes were insignificant. All these observations revealed an initial high proteol ysis 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 ti ssues the degree of proteolysis was in the order : liver > muscle > br ain.