Effects of Sustained-Release Delivery of Sodium Alginate Microsphere-Human Chorionic Gonadotropin (NaAlg-HCG) on Reproductive Hormones in Female Goldfish Carassius auratus (Linnaeus) var

Abstract:

The sustained-release delivery system of human chorionic gonadotropin (HCG) has been considered as a good method to induce gonad maturation in cultured fish. Sodium alginate microsphere is a new type of sustained-release delivery system of Human Chorionic Gonadotropin (NaAlg-HCG). In this study we implanted the NaAlg-HCG into female goldfish at regular intervals and examined its effects on the gonadal development, the level of major sex hormone in serum, and the expression of genes associated with reproduction hormones. The serum hormone level was measured with Radiate Immuno Assay (RIA) and the gene expression was examined using RT-PCR. Initially most oocytes of female golden fish were at stage III. From the Day 6 to Day 21 after the implantation, the gonadosomatic index (GSI) of fish implanted with NaAlg-HCG was significantly higher than that of the control group (P<0.05). From the Day 6 to Day 30, the levels of both estradiol (E2) and testosterone (T) in the serum of NaAlg-HCG group were significantly higher than those of the control group (P<0.05). RT-PCR results showed that from Day 6 to Day 21, the relative expression level of CYP19A of the NaAlg-HCG group was significantly higher than that of the control group (P<0.05). From Day 14 to Day 30, the ERα mRNA in the gonad of the NaAlg-HCG group was significantly higher than that of the control group (P<0.05). There was no difference in the relative expression level of GH in the gonad between the NaAlg-HCG group and control (P>0.05), except for the 2nd day after the implantation of NaAlg-HCG (P<0.05). These results suggested that after one-time implantation of NaAlg-HCG, HCG could be released steadily and regularly in 21 days. During this period NaAlg-HCG significantly increased the gonadosomatic index (GSI), the level of sex hormone in the serum, and the relative expression of genes associated with reproduction. The sodium alginate microsphere-based sustained-release delivery system therefore could be a good candidate for hormone implantation.