Abstract
This study investigated the influence of long-term T and 11-KT administration (by means of an implant) on the synthesis and release of gonadotropins (Fsh, Lh) and spermatogenesis progression in juvenile male sea bass exposed to either a natural photoperiod (NP) or continuous light (LL). The results in the control group indicated a clear role for Fsh and 11-KT in the recruitment of type-A spermatogonia (SPGA) towards more advanced stages of spermatogenesis under the NP regime. Fsh promoted androgen synthesis and SPGA differentiation into spermatocytes, while no significant changes in pituitary Gnrh1 and plasma Lh levels were detected. On the other hand, the LL regime inhibited Fsh synthesis, and although no effects were observed on Gnrh1 and Lh, the progression of spermatogenesis was arrested. T and 11-KT administration increased the Gnrh1 and Lh content and reduced the pituitary Fsh content, regardless of the photoperiod regime, although the inhibitory effect of T on pituitary Fsh was stronger than that of 11-KT. Our results show that exogenous 11-KT administration in fish under the LL regime was able to partially restore the progression of spermatogenesis, thus stimulating gonadal development and eliciting spermiation in a few fish, while males that received T implants remained sexually immature under LL. In addition, our results provided new knowledge about the importance of Fsh bioactivity modulation in the regulation of this gonadotropin function, and in turn, on spermatogenesis control in fish.
Highlights
Gametogenesis is a biological process under the influence of numerous factors that act in a hierarchical manner along the brainpituitary-gonadal axis (BPG), with the production of neuropeptides and neurotransmitters in the brain, gonadotropin hormones (Gths) in the pituitary and sexual steroids in the gonad and brain, all of this regulated by complex feedback mechanisms
We investigated the long-term effect of T and 11KT administration on the synthesis and release of Gths, gonadal growth (GSI) and spermatogenesis progression in juvenile male sea bass exposed to either natural photoperiod (NP) or LL photoperiod regimes during their early sexual maturation (Supplementary Fig. 1)
Previous studies on male sea bass have shown that plasma sex steroids, i.e. T and 11-K, peak in December–January (Rodríguez et al, 2000, 2001; Rocha et al, 2009), which agrees with the high levels of these steroids that we observed in January in the control group (NP sham implants)
Summary
Gametogenesis is a biological process under the influence of numerous factors that act in a hierarchical manner along the brainpituitary-gonadal axis (BPG), with the production of neuropeptides and neurotransmitters in the brain, gonadotropin hormones (Gths) in the pituitary and sexual steroids in the gonad and brain, all of this regulated by complex feedback mechanisms Besides this extraordinary performance, there is a strong interaction with environmental factors (photoperiod) in fish that contributes to the activation of the BPG axis and triggers sexual maturation (Schulz et al, 2010; Levavi-Sivan et al, 2010; Carrillo et al, 2015; Mazon et al, 2015). Fsh is able to rouse steroidogenesis during the initiation of spermatogenesis, inducing the production of 11-ketotestosterone
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
