Ultrastructural and morphometric study of the Sertoli cell of the viscacha(Lagostomus maximus maximus) during the annual reproductive cycle

Changes in the morphology of viscacha Sertoli cells were studied during the annual reproductive cycle. Sertoli cells exhibited marked nuclear and cyto plasmic changes. Seasonal variation in nuclear size and shape, chromatin te xture, and nucleolus characteristics was observed. The seasonal patterns of the volume densities of the endoplasmic reticulum (ER), mitochondria, Golg i complex, dense bodies and lipid inclusions were distinct. Morphometric an alysis revealed that the Golgi complex is the organelle most sensitive to s easonal change. It declined drastically in the regressed testes and its rec overy was slow. The ER and mitochondria exhibited seasonal variations in th eir pattern and content, that was minimal during winter. In contrast, an ac cumulation of lipid and dense bodies, such as primary and secondary lysosom es, accompanied the spermatogenic arrest. The volume densities of both orga nelles were maximum during the restoration of spermatogenesis. The length a nd organization of the inter-Sertoli junctions also changed with the reprod uctive cycle. The Sertoli cell number per tubular cross section decreased s ignificantly during the testicular regression, coincident with the presence of Sertoli cells with marked signs of involution. The degree of regression and recovery exhibited by the viscacha Sertoli cells was closely related t o that shown by the associated germ cells. Therefore, seasonal endocrine fl uctuations and local factors could be involved in the regulation of the mor phological and functional characteristics of the viscacha Sertoli cells. Th ese hormonal fluctuations are synchronized by the photoperiod through the p ineal gland and its hormone, melatonin. Anat Rec 262:176-185, 2001. (C) 200 1 Wiley-Liss, Inc.