THE PREPARATION OF RECOMBINANT GROWTH HORMONE AND ITS EFFECTS ON THE GROWTH OF JUVENILE IN PELTEOBAGRUS FULVIDRACO

In this study, the mature peptide-encoding cDNA sequence of the growth hormone of Pelteobagrus fulvidraco (PfGH) was inserted into the prokaryote expression vector pET-28a (+). The recombinant plasmid of pET-PfGH was then transfected into Escherichia coli BL21 (DE3) and was induced by IPTG. The SDS-PAGE results showed that E. coli BL21 (DE3) with pET-PfGH expressed a specific fusion protein with a molecular weight of 21 KD. The western blot test revealed that the protein contained a 6-His tag. PfGH was abundantly expressed in E. coli cultured at 17℃ for 14 hours with the final IPTG concentration of 1.0 mmol/L. After ultrasonic disruption the soluble recombinant protein was recovered and purified, and was then applied to juvenile Pelteobagrus fulvidraco. The subjects with the average weight of (0.850.01) g were randomly divided into four groups and were raised in an indoor aquarium. Every group had three repeats with 35 fish in each. The experiments were conducted in the interior circulation water purification system. During the 4-week feeding trial, four groups were soaked in liquid containing the recombinant GH at different concentrations of 0 (the control), 1 (group 1), 5 (group 2) and 10 mg/L (group 3) respectively, and the soaking frequency was once a week. At the end of the trial, our results showed that compared to the control group, the weight gain rate (WG) and the specific growth rate (SGR) of group 1 increased by 29.67% (P0.05) and 11.90% (P0.05) respectively; the WG and SGR of group 2 increased by 21.32% (P0.05) and 8.83% (P0.05) respectively. However, the body composition was not significantly different between the four groups. Furthermore, no significant difference was detected in the growth performance and the body composition between the four groups in 4 weeks after the cease of growth hormone treatment.