Is testosterone essential for maintenance of normal morphology in immature rat Leydig cells?

Selective deprivation of gonadotrophins in prepubertal rats by administration of a GnRH antagonist (Ac-D2Nal1, D4ClPhe2, DTrp3, DArg6, DA1a10-GnRH; GnRH code: 103-289-10, National Institutes of Health, USA) for 3 weeks, initiated at 20-22 days of age, induced morphological changes in the Leydig cells, including thickening and indentation of the nuclear margin, pyknosis and elongation of the nuclei. Mean nuclear diameter was reduced to 22% of that in the controls. Under the electron microscope the cells exhibited reduced volume of the nucleus and cytoplasm and the plasma membrane was irregular. This abnormal appearance of the Leydig cells improved marginally in 20-30% of the Leydig cells and their mean nuclear diameter increased to 39% of the control level after FSH supplementation (20 micrograms ovine FSH/day). Normal morphological integrity of the Leydig cells consisting of round or oval nuclei, a smooth nuclear and cellular margin and the original mean nuclear diameter was restored completely when testosterone (30 micrograms/day) was administered to GnRH antagonist-treated rats, with or without simultaneous administration of FSH; in these rats testosterone levels in blood were also restored to normal. These findings indicate that testosterone may be important for the maintenance of normal Leydig cell morphology in the rat.