Electron microscopic evidence for effect of androgens on the prepubertal differentiation of rat Leydig cells

Adult Leydig cells (LC) differentiate within the testis postnatally and there are three distinct stages in their development - progenitors, immature LC and mature type LC. Previous studies in rat have shown that both androgens and luteinizing hormone are involved in the differentiation of immature LC from LC progenitors. The present study aimed to investigate the ultrastuctural characterization of LC during the postnatal development of rat testis after in vivo treatment with testosterone. Male Wistar rats 14-days-old were treated for one week with testosterone. Animals receiving a daily vehicle injection were used as controls. The electron microscopic analysis showed that in the testicular interstitium of control rats a few elongated LC whose ultrastructure corresponded to that of progenitor type LC were observed. Compared to the control animals, in the rats treated with exogenous testosterone numerous interstitial cells with similar electron microscopic pattern to those of immature type LC were found. Our findings demonstrated an increased transformation of progenitors in immature LC after in vivo treatment with testosterone and indicated the role of androgens in the differentiation processes of LC during the rat postnatal development.