THE EFFECTS OF AMMONIA EXPOSURE ON AMINO ACID METABOLISM IN CHINESE LOACH PARAMISGURNUS DABRYANUS

To investigate the effects of ammonia exposure on amino acid metabolism, the Paramisgurnus dabryanus were exposed to 30 mmol/L NH₄Cl solution to assess plasma, liver and muscle free amino acid contents. The free amino acid concentrations in plasma, liver and muscle of P. dabryanus were significantly affected by ammonia expo-sure (P<0.05). The plasma free alanine contents significantly increased with increased exposure time (P<0.05). The liver free glutamate contents increased significantly at 12h of ammonia exposure and then obviously decreased at 72h (P<0.05). While the liver free alanine contents remained constant during the first 24h of ammonia exposure, these va-lues remarkably increased at 72h (P<0.05). The muscle free glutamate increased significantly (P<0.05) at 12 hours and then rapidly decreased (P>0.05), and eventually significantly lower than that of the control group at both 72h and 96h (P<0.05). Two peak values of the muscle free alanine contents were found at the 12h and 48h, which were significantly higher than the control values (P<0.05). The remarkably decreased free glutamate values in plasma, liver and muscle of P. dabryanus and the significantly increased glutamine contents and glutamine synthetase activities during ammonia exposure suggest that the glutamate and \rmN\rmH^ +_4 were synthesized into glutamine via glutamine synthetase under high environmental ammonia. With the increased exposure time, the accumulation of free alanine and significantly decreased free glutamate, arginine and proline revealed that P. dabryanus could use certain amino acid metabolism and the formation of alanine to inhibit the production of endogenous ammonia during ammonia exposure.