SECRETORY SYNTHESIS OF ACTIVE RECOMBINANT FISH GROWTH-HORMONE BY INSECT CELLS USING A BACULOVIRUS VECTOR

A growth hormone cDNA of yellowfin porgy (Acanthopagrus latus) was ins erted into baculovirus vectors, pAcT7, under the control of the polyhe drin promoter. A 22-kilodalton (kDa) protein, similar to that of nativ e growth hormone, was detected in the supernatant of insect cells infe cted with the recombinant virus at the level of 2-8% of total proteins . This protein was immunoprecipitated with rabbit polyclonal antibodie s raised against native chum salmon (Oncorhynchus keta) growth hormone . Furthermore, a radiolabeled protein band of 22 kDa was also seen in the recombinant-virus-infected cell culture supernatant after labeling with [S-35]methionine. Injection of individual tilapia with 0.1 mug o f crude supernatant protein containing recombinant growth hormone once a week resulted in significant increases (p < 0.01) in weight (54%), weight gain (260%), length (21%), and feed efficiency rate (210%) rela tive to a similarly treated control group and an untreated control gro up at week 5 onwards.