Cyclic changes in the testis and vas deferens of the rainbow trout (Salmo gairdneri) with special reference to sites of steroidogenesis

Abstract

Enzyme cytochemical and electron microscopical data indicate Leydig cells as the main source of steroids in the testis of Salmo gairdneri. Steroidogenesis in Leydig cells is found during the annual testis cycle, with a peak in activity from January to June, i. e. the period when the testes are mature and new primary spermatogonia are formed. In June, Leydig cells are mainly found around seminiferous tubules containing secondary spermatogonia. Enzymes involved in steroidogenesis are also present in Sertoli cells of November animals during spermiation. Steroid formation has furthermore been demonstrated in stroma cells distributed in the connective tissue around the epithelium of the vas deferens. Steroidogenic activity in these stroma cells is stronger in the period when sperm cells are stored in the lumen of the vas deferens.