Optimal conditions for determination of aspartate aminotransferase activity in rainbow trout and whitefish

Abstract

Aspartate aminotransferase (AspAT) activity is frequently used as a biochemical indicator offish physiological status, the clinical indicator of pathologies related to diseases and/or toxicity stress. However, there has been a lack of consensus on the optimal conditions for measuring AspAT activity in fish tissues and body fluids. In this study we used the spectrophotometric method recommended by the International Federation of Clinical Chemistry (IFCC) which was based on absorbance changes at 339 nm due to NADH oxidation, to test effects of L-aspar-tate, pH and presence of pyridoxal 5'-phosphate on AspAT activity in rainbow trout (Oncorhynchus mykiss) and whitefish (Coregonus clupeaformis) blood plasma and liver extracts. We also tested the effect of temperature at range 10–40°C on the liver AspAT activity and calculated the relationships of AspAT activities at various temperatures at range 10–30°C. Blood and liver AspAT activities were highest at pH 7.8. Liver activity was highest at 60 mM L-aspartate concentration. Pyridoxal 5'-phosphate stimulated activities in both tissues by 10–20 %. The IFCC method with few modifications is recommended for AspAT assay in fish and offers a replacement for the numerous AspAT assays currently in use.