Serum sex steroids and their specific cytosol binding in the pituitary and gonads of Russian sturgeon (Acipenser gueldenstaetdii Brandt) during final maturation.

Summary The study focussed at serum sex steroid concentrations in female and male sturgeons with gonads in maturity stages III and IV at the beginning of their anadromous river migration. Testosterone (T) levels were higher in males, than in females, and estradiol-17β (E 2 ) concentrations were higher in females than in males. After final maturation (induced by LHRH-A), T levels decreased in both sexes. E 2 concentrations were also lower in females after ovulation than prior to hormonal treatment. Specific cytosol binding of androgens (SBA) in the pituitary of female and male was higher at ovulation and spermiation than in untreated non-maturated fish. In spermiating males SB of estrogens (SBE) was significantly higher in the pituitary than in the ovulated females. Significant differences were elucidated in SBA and SBE in the ovary stroma before and after ovulation as well as in the testis before and after spermiation, after final maturation SB of sex steroids was much higher. Correlations between serum androgen and estrogen levels and their SB in pituitary and gonads before and after final maturation were established. The data demonstrated the role of these interactions in the reproductive function regulation in sturgeons (Chondrostei).