UP-REGULATION OF HEPATIC RECEPTOR FOR GROWTH HORMONE IN THE FLOUNDER （PARALICHTHYS OLIVACEUS） AFTER ORAL ADMINISTRATION WITH EXOGENOUS GH

The iodination efficiency of salmon GH (sGH) was 38.82%,using a modification of the chloramine-T method. The specific activity of the ^125I-sGH was about 40 μCi/μg protein. The results of binding assay showed a single class of high affinity and low-capacity binding site in flounder liver. Long-term administration with exogenous GH can induce the up-regulation of hepatic GH receptor in total binding capacity though there was no significant difference of association constant among any groups. Con-sidering that there was no significant difference in capacity of free binding sites of livers from control and experimental fish, this result also indicated that the liver from experimental fish, compared to that from control fish, had more occupied binding sites.     

Optimization of the purification methods for recovery of recombinant growth hormone from Paralichthys olivaceus

This study aimed to optimize the purification of recombinant growth hormone from Paralichthys olivaceus. Recombinant flounder growth hormone (r-fGH) was expressed by Escherichia coli in form of inclusion body or as soluble protein under different inducing conditions. The inclusion body was renatured using two recovery methods, i.e., dilution and dialysis. Thereafter, the refolded protein was purified by Glutathione Sepharase 4B affinity chromatography and r-fGH was obtained by cleavage of thrombin. For soluble products, r-fGH was directly purified from the lysates by Glutathione Sepharase 4B affinity chromatography. ELISA-receptor assay demonstrated that despite its low receptor binding activity, the r-fGH purified from refolded inclusion body had a higher yield (2.605 mgL-1) than that from soluble protein (1.964 mgL-1). Of the tested recovery methods, addition of renaturing buffer (pH 8.5) into denatured inclusion body yielded the best recovery rate (17.9%). This work provided an optimized purification method for high recovery of r-fGH, thus contributing to the application of r-fGH to aquaculture.     

GROWTH PROMOTION OF RED SEA BREAM, PAGROSOMUS MAJOR, BY ORAL ADMINISTRATION OF RECOMBINANT EEL AND SALMON GROWTH HORMONE

Recombinant eel GH and yeast containing chinook salmon growth hormone (reGHand rcsGH) were incorporated into gelatin and sodium alginate (reGH-GS and rcsGH-GS) or polymer ma-trix (reGH-HP55) to protect the hormone from proteolytic cleavage in the stomach. The diets containin greGH-GS, rcsGH-GS, reGH-HP55 and free-reGH or uncoated-rcsGH were administered to red sea bream. Feeding of reGH-GS, reGH-HP55 and rcsGH-GS diets resulted in significant increases in body weight and fork length over those of controls. These results strongly suggest that gelatin and sodium algi-nate as well as polymer matrix protected the hormone from proteolytic enzymes in the gastrointestinal tract to allow the bioactive hormone to enter the circulation and eventually stimulato fish growth.     

The effects of recombinant eel growth hormone,methyltestosterone and L-thyroxine on the growth of red sea bream,Pagrosomus major

the effects of recombinant eel growth hormone (reGH), methyltestosterone (MT) and L-thyroxine (T4) on the growth of red sea bream,Pagrosomus major, were investigated. Administration of reGH to fry by immersion at 2 mg/1 for 2 h every 5 days resulted in significant increase in both weight and length, but the condition factor (CF) diminished relative to that of similarly treated controls over the 37 day treatment period. Immersion in 0.1 mg/l T4 also resulted in significant increase in both weight and length and higher survival rate of test fry compared to the controls. Immersion in MT had less effect on growth and high-dose resulted in high mortality. In the second study, injection of 2 μg reGH/(g·wk) caused a significant increase in the specific growth rate (SGR) of test red sea bream fingerlings relative to that of the controls during the 4—week treatment period and maintained the increasing trend over the post-treatment period (weeks 4–6). Injection of MT at a dosage of 1μg/(g·wk) resulted in a significant increase in SGR during the 4—week treatment period. Intramuscular injection of 0.1 μg T4/(g·wk) also resulted in a significant increase in weight. Injection of high-doses of MT and T4 inhibited growth and resulted in darkening skin, bulging eyes and thinning body. In muscle chemical composition, the treated groups had no significant differences compared to the controls, but the high-dose MT and T4 groups showed significant increases in lipid content. Potential practical methods for hormone application in fish culture are discussed.     

Single nucleotide polymorphisms in intron 1 and intron 2 of Larimichthys crocea growth hormone gene are correlated with growth traits

The growth hormone gene (GH) affects animal growth and is a potential target for genetic studies of variation related to growth traits. In this study, we analyzed single nucleotide polymorphisms (SNPs) in GH intron regions and their associations with growth traits in large yellow croaker, Larimichthys crocea, from Zhejiang and Fujian stocks. The results of PCR-single strand conformation polymorphism showed two haplotypes of intron 1, named AA and AB genotypes, in Zhejiang stock. AB exhibited an SNP at position 196 (G A) that was negatively correlated with body height and positively correlated with standard length/body height (P 0.05). Two different genotypes, CC and CD, were identified in intron 2 in Fujian stock, with CD showing an SNP at position 692 (T C). The CD genotype had a significantly positive correlation with both weight and total length (P 0.01). These basic data highlight the potential for using GH as a genetic marker of fish growth in marker assisted selection.