Treatment of GnRHa-implanted Senegalese sole (Solea senegalensis) with 11-ketoandrostenedione stimulates spermatogenesis and increases sperm motility

The effect of 11-ketoandrostenedione (OA) on plasma concentrations of sexual steroids and spermatogenesis of Senegalese sole (Solea senegalensis) implanted with gonadotropin-releasing hormone agonist (GnRHa) was investigated. Males were treated with saline (control) or with GnRHa implants (50 μg kg− 1) in the presence or absence of OA (2 or 7 mg kg− 1) during twenty eight days. Treatment with GnRHa alone slightly stimulated spermatogenesis and milt production with respect to controls, and this was associated with a transient elevation of plasma 11-ketotestosterone (11-KT) at day seven and an increase of 5β-reduced metabolite(s) of 17,20β-dihydroxy-pregn-4-en-3-one (17,20βP) at day twenty eight. However, treatment with GnRHa + OA increased plasma concentrations of 11-KT and free + sulphated 5β-reduced metabolites of 17,20βP at days seven, fourteen and twenty one. After twenty eight days, the testis of GnRHa + OA-treated fish showed a lower number of spermatogonia B and spermatocytes I, and a higher number of spermatids, than fish treated with GnRHa alone. In addition, the motility of spermatozoa produced by GnRHa + OA males was enhanced by 2-fold with respect to controls or GnRHa males. These results suggest that treatment of Senegalese sole with GnRHa + OA stimulates spermatogenesis resulting in more motile sperm. Such effects could be mediated by an increased synthesis of 11-KT and/or 17,20βP in the testis but further studies will be required to elucidate the specific mechanism involved.