Steroidogenic activity and morphological characterization of prenatal testes and epididymis of guinea pig (Cavia porcellus)

The present study aims to establish the morphological, morphometric, and immunostaining patterns of the steroidogenic enzymes 17β-HSD and 5α-reductase and androgen receptors (AR) during the prenatal development of the male gonad and epididymis of Cavia porcellus. Fetuses at 22, 25, 30, 40, 45, 50, and 60 days of gestation (DG) were used. Specimens were dissected and subjected to macroscopic, histological, histomorphometric, and immunohistochemical analyses. Genital and scrotal protrusions were identified in 22 DG embryos. Gonocytes were identified at 25 DG and the formation of primary testicular cords was observed at 30 DG. Through anatomical evaluation, we observed differentiation of the epididymis into the head, body, and tail at 45 DG. During development, there is a progressive decrease in the diameters of the testicular cords and epididymal ducts. 17β-HSD enzyme immunostaining was observed in Leydig cells at all ages, while 5α-reductase was observed in Leydig cell cytoplasm and gonocytes at 40, 50, and 60 DG. AR shows gonocyte labeling at 30 DG. Thus, from the second trimester of pregnancy, it is possible to observe patterns of anatomical development, such as genital and scrotal prominence (22 DG), the appearance of gonocytes in the testicular cords at 25 DG, and the beginning of the organization of primary testicular cords at 30 DG, suggesting sexual differentiation. The 17β-HSD, 5α-reductase, and ARs play an essential role in sexual development and differentiation, presenting immunostaining at different reproductive process times. •Genital and scrotal protrusions identified in embryos at 22 days of gestation.•Gonocytes observed at 25 days: formation of primary testicular cords at 30 days.•Epididymis differentiation (head, body, tail) observed at 60 days.•Diameters of cords and ducts decrease progressively during development.•Immunostaining of 17β-HSD, 5α-reductase, AMH, and AR revealed roles in sexual development.