Immunohistological localization of 17β-estradiol and testosterone in the ovary of the rainbow trout (Salmo gairdneri Richardson) during the preovulatory period

Antisera (AS) raised in rabbits against 17 β-estradiol (E) and testosterone (T) were tested for their suitability to localize E and T on deparaffinized, rehydrated sections of preovulatory trout ovaries, using the unlabeled antibody technique. Conventional control experiments demonstrated the specificity of the staining reactions. Furthermore, no staining was observed after the removal of T-specific antibodies by affinity chromatography, or following gonadectomy when non-gonadal tissue sections of male trout were incubated with T-AS. Antiserum, raised against 11-oxotestosterone and devoid of antibodies cross-reacting with T, did not stain ovarian sections. The loci at which E and T are detected in the somatic compartment are consistent with the two-cell concept of estrogen synthesis, where aromatizable androgens are produced in the thecal/interstitial layer and serve as substrates for estrogen synthesis in granulosa cells. Both steroids were detected in yolk vesicles from the stage of endogenous vitellogenesis. T-AS showed affinity for nuclei of vitellogenic oocytes. Nucleoli were not stained.