PURIFICATION AND PARTIAL CHARACTERIZATION OF THE VITELLOGENIN OF CORAL TROUT, PLECTROPOMUS-LEOPARDUS

Vitellogenin (VTG) of the protogynous hermaphrodite coral trout, Plect ropomus leopardus, was purified and partially characterized from the p lasma of estrogen-injected fish using hydroxylapatite column chromatog raphy followed by gel filtration on Sephacryl S-300. The molecular mas s of VTG was estimated to be 350 kD with the gel filtration, and 180 k D with SDS-PAGE under reducing conditions. These results suggest that the VTG of P. leopardus is a dimer. The VTG band on SDS-PAGE was stain ed with lipid and phosphorus specific stains. Crossed immuno-affino-el ectrophoresis using Concanavalin A and rabbit anti-VTG antibody (a-VTG ) revealed that VTG had affinity to this lectin, suggesting that the c arbohydrate chains of VTG have N-acetyl-D-glucosamine and glucose and/ or mannose residues. When the occurrence of VTG in the sera of fish fr om 2(+) to 4(+) were checked with single radial immunodiffusion using a-VTG, VTG was first detected from the fish of 4(+) age class (one out of 30 serum samples taken in April, five of 30 in June and four of 30 in September). This result suggests that some P. leopardus functioned as females and started vitellogenesis at this age under rearing condi tions.