Assessment of the role of testosterone in the rat gonads: Morphometrical and cytochemical analysis

Rat testes are composed of somatic cells, primarily Sertoli (SC), myoid (MC) and Leydig cells (LC), and germinal epithelium which gives rise to spermatozoa. Sertoli, myoid, and Leydig cells have androgen receptors, of which Sertoli and myoid cells are thought to be primarily responsive to testosterone. Adjacent to Sertoli and myoid cells are Leydig cells which are the primary source of testosterone (T). The aim of this study is to evaluate the effects of T on testicular somatic cell morphology and changes in protein synthesis profiles, using prenatally irradiated male rats (devoid of germ cells) that are, thus, Sertoli-cell enriched (SCE).

Mature SCE rats were treated with Leuprolide (Leupr.) a GnRH agonist, for six weeks to prevent release of LH and FSH from the pituitary, thus, indirectly blocking T production from Leydig cells in the absence of LH. Some SCE rats were treated with testosterone propionate (T.P.) or in combination with Leupr. Testis weight (with and without tunica albuginea) of Leupr. treated groups were reduced to 53% of SCE controls. Seminiferous tubule diameter of Leupr. treated animals was reduced to 70% of the control. Neither testicular weight not tubule diameter were maintained by T replacement in Leupr. treated animals. Testosterone levels were reduced to 30% of SCE controls with Leupr. Androgen replacement with or without Leupr. increased T levels 17 and 13 fold respectively. With Leupr., Leupr. + T.P., or T.P. alone there was a two fold decrease of LH concentration as compared to the SCE control. FSH levels of groups treated with Leupr. alone and in combination with T.P. showed 94% and 81% higher and lower values, receptively, when compared to SCE controls.

Leydig cells showed a severe morphological change in the Leupr. treated group and interstitial tissue had an abundance of unidentified cells. Myoid and Sertoli nuclear morphology was unaltered and no statistical difference in SC numbers were observed.

Protein profiles of the testicular tissue were analyzed using SDS-PAGE. A newly synthesized protein (36kDa) was secreted into the medium with Leupr. treatment. This protein was not observed in control, or in T.P. treated animals, but it was found occasionally in the Leupr. + T.P. treated group.

Results obtained in this study appear to indicate a direct effect of Leuprolide in somatic cell morphology and in changes of the protein synthetic profile.