Hormonal Regulation of Spermatogenesis (Current Topics in Molecular Endocrinology)

the long version

Hormonal regulation of spermatogenesis is reviewed. The main topics are: 1. hormones and hormonal target cells in the testis, 2. Leydig cells (luteinizing hormone, estrogens, androgens, prolactin, follicle stimulating hormone - FSH), 3. peritubular cells (androgens), 4. Sertoli cells (FSH, androgens) and 5. germ cells (androgens). Androgenic hormones are a major stimulus for spermatogenesis and the production of testosterone (by Leydig cells) is regulated by interstitial cell-stimulating hormone (ICSH). FSH and prolactin enhance Leydig cell responsiveness while estrogen appears to inhibit Leydig cell response to ICSH with respect to steroidogenesis. Androgens stimulate peritubular cell differentiation and the development of tubular contractions, and regulate (with FSH) Sertoli cell function. It is concluded that most hormonal effects on spermatogenesis are mediated through the Sertoli cell. Localization of androgen target cells in the rat testis was studied by autoradiographic techniques. Immature male rats were hypophysectomized at 35 days of age and 10 days later they were eviscerated and functionally hepatectomized. Tritiated testosterone was injected iv and the rats were sacrificed 1 or 3 hours later. The autoradiograms showed nuclear concentration of radioactivity in certain cells within the seminiferous tubule and the interstitium. In some tubules cells of the basal layer concentrated little radioactivity when compared with 2nd and 3rd layers. Peritubular myoid cells and inerstitial cells concentrated radioactivity in their nuclei and cells in the tunica albuginea also showed labeling. Nuclear accumulation of radioactivity was abolished when cyproterone acetate was administered in 150-fold excess of tritiated testosterone. In immature androgen-insensitive rates, radioactivity did not accumulate in nuclei of seminiferous tubular epithelial cells, peritubular cells, or interstitial cells. Following the injection of tritiated estradiol, nuclear concentration of radioactivity was seen only in interstitial cells. Following the injection of tritiated dihydrotestosterone, nuclear concentration of radioactivity was seen in interstitial cells and tubular epithelial cells. These results suggest the existence of several different types of androgen target cells in the testis and nuclear accumulation of radioactivity in interstitial cells and myoid cells suggests a direct action of androgen on these extratubular cells.