IMMUNOASSAY AND PARTIAL CHARACTERIZATION OF SERUM TRANSFERRIN FROM ATLANTIC SALMON (SALMO-SALAR L)

Atlantic salmon (Salmo salar L.) serum transferrin was purified by riv anol precipitation followed by anion exchange liquid chromatography an d polyacrylamide gel electrophoresis. Transferrin was identified by ra dio-iron and analysed by amino terminal sequencing. Electrophoresis sh owed isoforms of transferrin both on native and denaturating polyacryl amide gels. All isoforms had identical amino terminal sequences and si alic acid linked to galactose. Removal of sialic acid groups by neuram idase treatment of single and mixed transferrin isoforms revealed five different charge forms suggesting the presence of up to four sialic a cid residues on Atlantic salmon serum transferrin. Polyclonal and mono clonal antibodies against salmon transferrin were produced and used in an enzyme-linked immunosorbent assay (ELISA). The sensitivity of the assay is high with the lowest detectable transferrin concentration bei ng 0.5-1 ng ml-1. No cross activity of the assay with serum from horse , rabbit or rainbow trout could be detected. The within-assay variabil ities were 2.5 and 7% when assayed within and between dilutions of the Atlantic salmon serum samples, respectively.