Sex steroids in the serum of Caspian sturgeons and their specific cytosol binding in brain and gonads during the migratory cycle

Testosterone (T) and estradiol 17 beta (E2) concentrations were measured in the serum of Russian, stellate and beluga sturgeons. Hormone concentrations were comparatively low during the feeding period at sea and did not differ between seasons or species. At the beginning of the spring spawning migration into freshwater, both of the spring and winter races of Russian sturgeon (Acipenser gueldenstaedtii) and beluga sturgeon (Huso huso), as well as the spring-summer race of stellate sturgeon (Acipenser stellatus), exhibited a marked elevation of serum T? despite differences in their degrees of gonadal development. There were no differences in specific cytosol binding of androgens and estrogens in the forebrain of either migratory form of Russian sturgeon, while the specific binding of sex steroids was higher in the hypothalamus of the spring form. The data indicate that T and its receptors may control aspects of anadromous migration in sturgeons.