HORMONAL-REGULATION OF SERTOLI-CELL DIFFERENTIATION

This study was carried out to determine the possible hormone dependence of the postnatal changes on the cytological characteristics of the rat Sertoli cells. Neutralizing antisera to rat follicle stimulating hormone (AS/FSH) and sheep luteinizing hormone (AS/LH) were prepared in rabbits and made monospecific by suitable absorption. Groups of male Sprague-Dawley rats were injected from birth to 32 days with either AS/FSH, AS/LH, AS/LH + testosterone propionate (TP), or normal rabbit serum (NRS). In control 33-day-old animals, Sertoli cells displayed most of the fine structural characteristics of the adult type. Their nuclei were highly infolded and showed an elaborate shape. Euchromatin was largely predominant with a few heterochromatic masses associated with the nuclear envelope or with the prominent nucleolus. The perinuclear area of cytoplasm was particularly rich in mitochondria, smooth endoplasmic reticulum (SER) and Golgi complexes. Inter-Sertoli cell junctions were fully developed. After AS/LH treatment, the nuclei were reduced in size and adopted a smooth surface with very few infoldings. In addition, many clumps of hetero-chromatin were apparent close to the nuclear envelope and the number of the nucleoli was reduced. Sertoli cell cytoplasm was severely atrophied following AS/HL administration, showing sparse mitochondria, SER and Golgi profiles. Addition of TP to the AS/LH treatment failed to reverse these cytoplasmic changes but resulted in a reappearance of the membrane infoldings of the nuclear envelope and normal numbers of nucleoli. On the other hand, AS/FSH treatment did not induce any apparent morphological change in the Sertoli cell nuclei. The cell volume was reduced but most of the cytoplasmic organelles were apparently present in normal numbers. However, extensively dilated cisternae of the endoplasmic reticulum containing floccular material were a common and impressive change. No modifications were detected in the Sertoli cell junctions in any of the experimental groups. ABP testicular and epididymal levels were diminished in both AS/FSH and AS/LH treated groups, but the reduction was more marked in the latter. ABP levels remained low when TP was administered with the AS/LH. These observations indicate that in the absence of LH morphological differentiation and growth of Sertoli cells are severely inhibited and that FSH withdrawal causes specific changes in the ER that may indicate a trophic action on it. The failure of TP to reverse the effects of AS/LH administration could be attributed to the possibly severe FSH inhibition induced by the high testosterone plasma levels.