The effects of 11-ketotestosteroneimplants on transcript levels of gonadotropin receptors, and foxl2 and dmrt1 genes in the Previtellogenic ovary of cultured beluga (Huso huso)

Thein vivoeffect of 11-ketotestosterone (11KT) on transcript levels of the gonadotropin receptors (fshrandlhr) and sex differentiation-related genes (dmrt1andfoxl2) was examined in the ovaries of immature female beluga. For this purpose, six fish were treated with implants containing 2.5 mg 11KT and a placebo group of six females of the same age and gametogenic stage were given a blank implant. The implants were intraperitoneally inserted into 4-year-old females at the previtellogenic stage (mean body weight 5580 +/- 165 g) and maintained under culture conditions for 8 weeks. Ovary samples for gene expression analysis oflhr,fshr,dmrt1andfoxl2were collected by biopsy at 3 and 8 weeks post implantation. Diameters of oocytes increased in response to 11KT treatment, both at 3 and at 8 weeks post implantation, but no obvious changes were evident in cytology. Three weeks of 11KT treatment did not affect target gene expression, but a tendency for a time-dependent decrease oflhranddmrt1mRNA levels was observed in both treatment and placebo groups. By 8 weeks of treatment, however, 11KT implants provoked the upregulation offshrandfoxl2transcript levels. Furthermore,lhranddmrt1transcript abundances recovered by 8 weeks of exposure in both blank- and 11KT-implanted beluga. These results suggest that 11KT, either directly or indirectly, may affect gametogenesis and regulate some key components of the reproductive axis in female beluga.