Assessment of serum protein fractions in rainbow trout using automated electrophoresis and densitometry

Although rainbow trout (Oncorhynchus mykiss, Walbaum) are one of the most-studied fish, electrophoretic techniques and classification of serum protein fractions have not been standardized, such that clinically useful values are lacking. The aim of the present study was to evaluate preliminarily the serum protein fractions of rainbow trout using automated cellulose acetate electrophoresis and densitometry. Serum samples from 25 rainbow trout (Oncorhynchus mykiss, Walbaum) were electrophoresed on cellulose acetate plates and quantified using densitometry. A maximum of 6 fractions were identified and numbered, in order of decreasing mobility, as I, II, III, IV, V, and VI. In 3 of 25 (12%) samples, 6 fractions were identified; in 18 (72%) samples, 5 fractions were identified; and in 4 (16%) samples, 4 fractions were identified. Fractions I, V, and VI were always clearly identifiable, whereas fractions II and IV were frequently fused and indistinguishable from fraction III. The pattern with 5 fractions was the most probable type (chi(2), P <.01). The mean (+/- SEM) protein concentrations of the 6 fractions were I, 0.8 +/- 0.1 g/dL; II, 0.3 +/- 0.0 g/dL; III, 1.6 +/- 0.1 g/dL; IV, 0.3 +/- 0.1 g/dL; V, 0.6 +/- 0.0 g/dL; and VI, 0.2 +/- 0.0 g/dL. Based on comparison of serum and plasma electrophoretic patterns from 8 fish, fibrinogen was found in fraction V. Automated cellulose acetate electrophoresis and densitometry appear to be a practical method for estimation of serum protein fractions in rainbow trout.