Testosterone immunoreactivity in rainbow trout (Salmo gairdneri Richardson) testis

Testosterone antiserum raised in rabbits according to conventional techniques was used to localize immunoreactive material in fixed, paraffin-embedded rainbow trout testis. Spermatogonia showed a nuclear label throughout the reproductive cycle; their nucleoli were not stained or stained less intensely. Spermatocytes displayed a staining of large cellular areas, showed an irregularly delineated intracellular label, or remained unstained; similarly stained spermatocytes were arranged in groups. Spermatids remained unstained. Spermatozoa were not labeled or were weakly labeled, which varied from male to male and also between different areas of a section. Sertoli cells showed a label confined to the nucleus. During active spermatogenesis they also carried a cytoplasmic stain. Interstitial cells with a cytoplasmic stain were found only rarely. The spermatocyte I/II transition is associated with the most considerable changes in the intracellular staining pattern.