| The physiological activities of the fish are regulated by the hypothalamus-pituitary-gonadal axis. Hypothalamic secretion of gonadotropin-rel easing hormone (gonadotropin-releasing hormone, GnRH) and other neuroendocrine factors, stimulate the secretion of pituitary gonadotropins (gonadotropic hormone, GtH), it can stimulate the gonads to produce sex steroid hormones contributing to the gonadal development and maturation, and expel the sperm and egg. However, the generation and emission of fish neuroendocrine factors are the effects of changes in the external environment factors. The main reason that farmed fish are usually unable to reproduce is due to changes in environmental conditions which can affect the pituitary gland not to secret a large number of GtH. In recent years, with the expansion of the scale of farming, given the hormone sustained-release formulations (in sustained-release delivery systems, the SRDS) become one method of induced sexual maturation and reproductive in the fish which are gonadal dysgenesis. In this research, we produced sustained-release formulations of the matrix and the LHRHA-release formulations and HCG sustained-release formulations,also we implanted these SRDS into goldfishes. By detecting related indicators such as basic biology:the gonadal index (GSI), hepatosomatic index (HSI), fish serum testosterone (T), estradiol (E2) levels, fish reproductive growth related gene mRNA relative expression level in the gonads, we evaluated the performance of sodium alginate and chitosan, as a sustained release formulation matrix in order to provide guidance for the production and provide a theoretical basis for the development of new sustained-release formulations1. The effect of sustained-release formulations on the the goldfish basis of biology.The male and female goldfish GSI did not produce significant differences with control group within48d after implantation of alginate microspheres and chitosan microspheres as the matrix. The trend after the implantation of two materials show consistency with the control group; Male and female goldfish HIS in the sustained-release matrix implants were not significant differences with the control group, the HIS in each group was showing an upward trend throughout the whole experimental period.The groups implantation with LHRHA-alginate microspheres, LHRHA chitosan microspheres, HCG-alginate microspheres and HCG-chitosan microspheres in the experimental period the trend showed a same trend:first increased and then decreased. Sustained-release Hormone affected GSI of goldfish from21d to30d after implantation. The time was longer than the control group. The female fish and the male fish had the same trend. The HIS has no significant difference between the fish which implanted Sustained-release Hormone and the fish which did not implant. Each group showed a increasing trend.2. The effect of sustained-release formulations on serum hormone levels of the goldfishAfter the implantation of alginate microspheres and chitosan microspheres, the male and female goldfish serum testosterone (T) and estradiol (E2) did not produce significant differences with control group. And throughout the experiment, serum hormones showed a downward trend with a minimum in21d or30d after implants.LHRHA-sustained-release formulations, HCG-sustained-release showed a similar trend in female and male goldfish. The trend declined after increasing which showed a significant differences compared with the control group. The duration of action was longer than one-time hormone implants in male and female goldfish. The highest value of the serum testosterone (T) and estradiol (E2) appeared in the14-2Id after implanting in the group of the sustained-release formulations3. The effect of sustained-release formulations on the expression level of mRNA of the goldfishAfter the implantation of drug-unloaded alginate microspheres and chitosan microspheres, the relative expression of CYP19A gene mRNA didn’t show significant differences with the control group in the goldfish gonads, and showed a consistent trend in the experimental process. The relative expression level of GH gene mRNA didn’t show significant difference with the control group in the gonads of female goldfish, after the implanted alginate microspheres. After implanting chitosan microspheres, the relative expression level of GH gene mRNA showed significantly higher in0-30d than control group in the gonads of female goldfish. The relative expression levels of GH mRNA didn’t show significant differences in male goldfish, after the implanted of sodium alginate microspheres and chitosan microspheres with the control group.LHRHA-sustained release formulations and HCG-sustained-release formulations showed a similar affect of male and female goldfish, and showed some correlation with serum hormone levels. Each treatment group showed a trend of first increased and then decreased after the implantation, and showed significant differences with the control group. Hormone sustained-release formulations displayed a longer action time in CYP19A gene and ERa gene of goldfish gonadal compared to one-time hormone implantation.Related test results indicated that sustained-release hormone plays an important role in the process of fish breeding, without affecting the growth of normal fish. The effects of fish showed remarkable persistence and stability compared to those without sustained-release hormones. |
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