IS TESTOSTERONE ESSENTIAL FOR MAINTENANCE OF NORMAL MORPHOLOGY IN IMMATURE RAT LEYDIG-CELLS

Selective deprivation of gonadotrophins in prepubertal rats by adminis tration of a GnRH antagonist (Ac-D2Nal1, D4ClPhe2, DTrp3, DArg6, DA1a1 0-GnRH; GnRH code: 103-289-10, National Institutes of Health, USA) for 3 weeks, initiated at 20-22 days of age, induced morphological change s in the Leydig cells, including thickening and indentation of the nuc lear margin, pyknosis and elongation of the nuclei. Mean nuclear diame ter was reduced to 22% of that in the controls. Under the electron mic roscope the cells exhibited reduced volume of the nucleus and cytoplas m and the plasma membrane was irregular. This abnormal appearance of t he Leydig cells improved marginally in 20-30% of the Leydig cells and their mean nuclear diameter increased to 39% of the control level afte r FSH supplementation (20 mug ovine FSH/day). Normal morphological int egrity of the Leydig cells consisting of round or oval nuclei, a smoot h nuclear and cellular margin and the original mean nuclear diameter w as restored completely when testosterone (30 mug/day) was administered to GnRH antagonist-treated rats, with or without simultaneous adminis tration of FSH; in these rats testosterone levels in blood were also r estored to normal. These findings indicate that testosterone may be im portant for the maintenance of normal Leydig cell morphology in the ra t.