EFFECT OF GROWTH-HORMONE ON THE GROWTH-RATE OF THE GILTHEAD SEABREAM (SPARUS-AURATA), AND USE OF DIFFERENT CONSTRUCTS FOR THE PRODUCTION OF TRANSGENIC FISH

When bovine or human growth hormones (GH) were injected into 6 months old (about 10 g) gilthead seabream, the growth rate of the fish, as measured by changes in their weight, increased by only about 15% compared with the saline-injected control. No effect or even slight inhibition of the growth rate was obtained when chicken or porcine GHs were injected. In a preliminary experiment, it was found that injection of the native GH increased the growth rate of the fish by about 20% after treatment for only 2 weeks. An expression vector, using the pRE1 plasmid and transformation into MZ1 cells, produced the gilthead seabream GH, providing a supply for further experiments on the effect of the homologous GH on growth. Two reporter genes, beta-galactosidase (lacZ) and melanoma oncogene of Xiphophorus (mrk YY), were microinjected into fertilized eggs of S. aurata. Expression of these two genes could be demonstrated in 2-day-old embryos, the lacZ gene by staining of its enzymatic product, and the mrk YY gene by its phenotypic expression.