Organization of the internal membrane system in the principal cells of the mouse epididymis after osmium impregnation

Abstract

Summary. The ultrastructure of the principal cells of the mouse epididymis was studied using osmium impregnation techniques which have the advantage that the endoplasmic reticulum (ER) content displays a positive reactivity after glutaraldehyde fixation whereas the Golgi condensing vacuoles are negative.In the proximal part (caput) of the epididymis, the Golgi apparatus formed a large supranuclear area filled with electronluscent secretory vacuoles while, in the medial (corpus) and distal (cauda) parts, dictyosomes were small and sparse with few secretory vacuoles. In all the principal cells of the caput, the supranuclear ER cisternae were heterogeneously impregnated. In the corpus and cauda, the ER appeared as an extensive continuous network of canaliculi and saccules which were fenestrated when surrounding mitochondria. The ER content was homogeneously stained but impregnation intensity varied from cell to cell. In the apex of the caput cells, numerous impregnated or electronluscent vesicles were seen in close apposition to the plasma membrane, while in the corpus and cauda some Golgi vacuoles and extensions of ER canaliculi were observed in the terminal webb region. Thus, in the epididymal caput, osmium impregnation suggested that two distinct secretory pathways were functioning continuously. The first corresponded to the transport of proteins to the cell membrane by the Golgi condensing vacuoles. The second might only affect the small impregnated vesicles of the ER, through which proteins bypassed the Golgi apparatus and were exported towards the lumen. In the corpus and cauda, the network organization of the ER and the association of fenestrated cisternae with mitochondria (also found in absorptive epithelial cells) supported the view of a predominant absorptive function in these epididymal parts.Introduction.

Development of the caput epididymidis studied by expressed proteins (a glutamate transporter, a lipocalin and ?-galactosidase) in the c-ros knockout and wild-type mice with prepubertally ligated efferent ducts

“…Attempts at three-dimensional reconstruction of the caput lobules together with epithelial cytology have produced either three (Takano 1980) or five (Abou-Haila and Fain-Maurel 1984) histologically distinct regions, the latter division being based on differences in osmium impregnation of the Golgi apparatus (Fain-Maurel et al 1988). Thus, confusingly, region II and region III of Takano (1980) are, respectively, synonymous with regions II and III, and regions III and IV, of Abou-Haila and Fain-Maurel (1984).…”