| Summary: | 碩士 === 輔仁大學 === 生物學系 === 88 === Growth hormone (GH), a protein secreted from the pituitary gland, plays important roles in many respects of physiological regulation, including growth, development, reproduction and metabolism, as well as osmotic regulation in fish. The expression of GH gene is mainly regulated by a pituitary transcriptional factor, Pit-1. It is reported that the expression of GH and Pit-1 can be detected in early embryonic stages. Even in placenta and ovary, the expression of these two genes can be detected, also. In this study, we performed the whole mount in situ hybridization and immunohistochemical method to follow up the expression of GH and pit-1 genes during the fish developmental stages, and to clarify if the earliest expression of GH gene is due to the maternal effect.
In this study, we used zebrafish (Danio rerio) to detect the GH gene expression during the embryonic development. We also used ayu( Plecoglossus altivelis ) as an animal material to detect the expression of GH and pit-1 genes. During the zebrafish embryonic developmental stages, we observed GH mRNA as early as one-cell stage, and through 36 to 45 hours post-fertilization ( pharyngula stage) in which the GH mRNA was detected in the middle region of brain. In ayu, the pit-1 mRNA was detected in the middle region of brain on day 5 post-fertilization, and GH mRNA was detected in the same site on day 9 post-fertilization.
By immunohistological study of the ovary from adult zebrafish, GH gene expression was also detected in various maturation stages of oocytes. In addition, GH mRNA was also detected in manually collected mature zebrafish eggs. On the other hand, in 3-day old ayu fry, Pit-1 protein was detected in the middle region of brain, as well as the region between the vertebral and the abdominal site.
According to the results, we suggested that during fish development, GH firstly expresses in maternal ovary and is transmitted to mature oocytes vertically to supply sufficient GH to eggs. Along with the embryo development, the pituitary gland matures and expresses GH. Moreover, Pit-1 may also involve in the tissue-specificity of GH gene expression in the ovary and pituitary glands.
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