Free amino acids in whole blood and plasma of two cyprinids, Cyprinus carpio and Carassius auratus (Cyprinidae: Teleostei)

Abstract

1. 1. Free amino acids were measured using a reversed-phase HPLC system in whole blood, plasma and erythrocytes of two fresh water cyprinids ( Cyprinus carpio, the common carp and Carassius auratus, the goldfish). 2. 2. Free amino acid recoveries were determined for whole blood, plasma and erythrocytes. Recoveries were high (80–90%) and were used for correction of free amino acid amounts in the biological samples. 3. 3. Taurine (2-aminoethanesulfonic acid) is the most common free amino acid in common carp and goldfish blood (respectively 9.2 and 5.5 mmol/1); the total amount of “protein-derived” free amino acids in whole blood of the common carp is significantly higher than that of the goldfish (5.3 ± 0.6 mmol/1 versus 3.9 ± 0.2 mmol/1; P < 0.01). The same holds for plasma free amino acids (common carp: 5.0 ± 1.0 mmol/1; goldfish: 3.6 ± 0.3 mmol/1). 4. 4. In these cyprinids, the essential free amino acids are more concentrated in the plasma, while the acidic free amino acids, as well as taurine and glycine, are restricted to the red blood cells. 5. 5. Some data on the free amino acid pools in the blood compartments of the crucian carp ( Carassius carassius) and the tilapia ( Sarotherodon mossambicus) show that the amino acid pattern of Carassius auratus is close to the other cyprinids but that tilapia has a far different pattern.