In vivo effects of GnRH peptide on gonadal proliferation and related gene expression of Pacific abalone, Haliotis discus hannai

Abstract

Gonadotropin-releasing hormone (GnRH) is a key hypothalamic neuropeptide regulating the reproductive function of vertebrates and invertebrates. In the present study, we report the role of GnRH in gamete cell proliferation of Pacific abalone, Haliotis discus hannai using BrDU incorporation, and analyzed the expression of reproductive responsive genes. In vivo injection of buserelin and H. discus hannai GnRH peptides (GnRH-I and GnRH-II) at doses of 250 and 500 ng/g BW resulted in a significant increases in the number of testicular and ovarian proliferating cells. Administration of GnRH peptide at higher doses was less effective in stimulating gonadal cell proliferation. A qPCR analysis revealed that the mRNA expression of GnRH, GnRH-R, and serotonin-R was elevated in the male gonad compared with female gonad in all treatment groups. Compared with control and other treatment groups, the expression profile of GnRH, GnRH-R, and serotonin-R was significantly higher after treatment with buserelin and synthetic GnRH peptides at doses of 250 ng/g BW in both male and female gonad. However, the gonadal tissues expressed lower levels of mRNA following the treatment with GnRH peptide at the higher dose (1000 ng/g BW). Furthermore, the results of comet assay demonstrated that gonadal cells did not show significant differences in the average level of fragmented DNA and tail length between control and treated groups. Taken together, these findings suggest that administration of GnRH peptide at a concentration of 250 ng/g BW effectively accelerated the gametogenesis of abalone. This strategy will enhance the benefits of breeding technology in this species, or may useful for increasing the aquaculture production.