The ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat epididymis

Abstract

The ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat caput epididymidis was examined with the electron microscope. Specializations of the principal cells associated with absorption include numerous endocytic invaginations of the cell surface, numerous coated vesicles and multivesicular bodies in the apical cytoplasm. It was demonstrated that particulate tracers are taken into the cells and sequestered in secondary lysosomes and multivesicular bodies. Morphological features consistent with secretory activity are also found in the principal cells and include numerous cisternae of rough endoplasmic reticulum with a flocculent grey content and an extremely well-developed Golgi apparatus. The speculation that the principal cells are actively secretory despite the absence of secretory granules formed in the Golgi and of a visible mechanism for release of the product at the cell surface is discussed.The "halo cells" in the epididymal epithelium were also examined and it is shown that many of these cells are not typical migratory lymphocytes, Chief among the differences are their granule-containing multivesicular bodies and more abundant endoplasmic reticulum. Nonetheless, it is conceivable that the halo cells are lymphocytes and that the conditions they encounter as they leave the circulation and enter the epididymal epithelium may stimulate morphological changes. The possible immunological significance of these observations is discussed.There have been several descriptions of the ultrastructure of the epididymal epithelium in recent years (Nicander, '65; Friend and Farquhar, '67; Flickinger, '69; Hamilton, '72a,b). The improved preservation and higher resolution achieved in these studies have corrected a number of persistent misconceptions of early light microscopists who worked on the epididymis. Thus, irregular surface protrusions previously interpreted as a manifestation of apocrine secretion have been shown to be artifacts of fixation and certain granules formerly regarded as secretory products have been shown to be lysosomes. The structural differentiation of the cytoplasm has proven to be far more elaborate than previously supposed and it is quite evident that this eoithelium is by no means the metabolically inactive lining of an organ for sperm storage. The functional corre-ANAT. REC., 175: 169-202.lates of the cytological features are largely unknown, and, although considerable evidence is available on the morphology of the absorptive process in principal cells (Friend and Farquhar, '67; Nicander, '65; Burgos, '64), the morphology of secretion of glycerophosphorylcholine (Dawson, Mann and White, '57; Dawson and Rowlands, '59), carnitine (Marquis and Fritz, '65), sialic acid (Rajalakshmi and Prasad, '69) or steroids (Hamilton et al., '69; Hamilton, '72b) has not been elucidated.In the present paper we report the mor-

La segmentation du canal épididymaire chez la souris : étude ultrastructurale

“…En dépit de la richesse en réticulum endoplasmique lisse des cellules dans certaines espèces la synthèse de stéroïdes dans l'épithélium épididy-maire n'a été démontrée qu'in vitro (Hamilton et Fawcett, 1970). En revanche, la captation de la testostérone par l'épididyme et sa conversion en 5a-dihydrotestostérone ont été mentionnées, en particulier au niveau de la tête (de Larminat et al, 1980 Dym, 1977), le rat (Hoffer et al, 1973) et le hamster (Flickinger et al, 1978), sont considérées comme des lymphocytes intraépithéliaux. Les cellules apicales ont été décrites chez le singe (Ramos et Dym, 1977), les cellules claires chez le hamster (Flickinger et al, 1978 …”

Características regionais sobre a ultra-estrutura das células principais do epitélio do ducto epididimal de Agouti paca

“…Cisternas com aparência vesicular, presentes principalmente nas células principais do epidídimo de paca, e de outros mamíferos 5 , foram identificadas como cisternas dilatadas do RE, que têm poucos ribossomos aderidos 6 , talvez tendo uma possível implicação na secreção de proteínas 18 .…”

“…2,3,4 Aparentemente, proteínas, secretadas pelo RER de células epididimárias, poderiam ser liberadas diretamente no lúmen epididimário. 18 Por outro lado, a secreção de proteínas passaria, diretamente, através do aparelho de Golgi, antes de ser liberada no lúmen tubular. 21 Porém, estudos autoradiográficos, com isótopos marcados, mostraram os grãos de prata inicialmente sobre o RER e sucessivamente sobre o aparelho de Golgi; superfície celular apical e lúmen tubular.…”

Zinc Iodide-Osmium Tetroxide (ZIO) Reactive Golgi Apparatus in the Principal Cells of Dog Epididymal Epithelium

“…Hamilton and Robaire & Hermo postulated that these cells secreted of a variety of substances, such as ions, small organic molecules, and glycoproteins,which have been suggested to have a role in sperm maturation. Hoffer et al (1973) and Ramos & Dym have suggested that the principal cells of the mammalian epididymis perform synthesis and secretory activities, based on the presence of numerous rough endoplasmic reticulum lamellae and a well-developed Golgi apparatus.…”