Stimulation of interstitial cell growth after selective destruction of foetal Leydig cells in the testis of postnatal rats

Five-day-old male rats received a single treatment of ethane dimethanesulphonate (EDS), and the response of the testis on days 6-10 and 21 was examined by light microscopy and morphometry, supplemented by measurement of peripheral testosterone levels. One day after treatment, foetal Leydig cells degenerated, showing fragmentation, condensation and nuclear pyknosis. Macrophages phagocytosed the foetal Leydig cells resulting in their disappearance by day 7. Destruction of foetal Leydig cells was followed by an arrest of testicular growth in comparison to testes of intact age-matched control rats. In testes of EDS-treated rats, gonocytes and spermatogonia also degenerated, forming pyknotic bodies within the seminiferous cords. In contrast, interstitial fibroblasts and mesenchymal cells showed proliferative activity, which on days 4 and 5 after treatment resulted in peritubular hyperplasia surrounding each seminiferous cord. Thereafter, on day 21 after EDS administration, the previously depressed serum testosterone levels became markedly elevated coincident with the development of many immature-type Leydig cells, of which the total volume per testis was similar to that of Leydig cells in control testes, despite a four- to five-fold difference in testicular volumes. The results indicate that, although EDS destroys the foetal Leydig cells and impairs spermatogenesis, the interstitial tissue exhibits increased cell growth. The latter probably occurs in response to altered gonadotrophic stimulation and/or disturbances in the interaction between the seminiferous cords and the interstitial tissue.