Effect of ammonia on respiratory functions of blood of Tilapia zilli

The present paper attempts an examination of different changes of blood respiratory properties when Tilapia zilli is exposed to ammonia in three sublethal concentrations (1.1, 2.2 and 3.3 mg NH3 l(-1)) for 2 weeks. The results revealed that oxygen and carbon dioxide partial pressures (P-O2 and P-CO2) were changed differently and irregularly both in the caudal artery and in the heart. The acid-base status (pH, HCO3-, TCO2 and base excess) of arterial and venous blood changed tc,wards alkalosis during the first week. These changes were exaggerated during the second week of ammonia exposure. O-2 saturation of arterial blood was decreased, while that of venous blood was increased due to the disturbances in blood gas transport and exchange mechanisms and in the acid-base status. The oxygen equilibrium curve was shifted to the left and P-50 was decreased during most of the experimental periods. (C) 1998 Published by Elsevier Science Inc. All rights reserved.