The intracellular pathway of antagglutinin secretion in the boar caput epididymidis as revealed by immunogold labelling

Summary Antagglutinin, a specific protein synthesized by the boar epididymis, was localized by an ultrastructural immunogold-labeling procedure in the principal cells of the three regions of the caput epididymidis, most notably at the sites of synthesis and secretion. The intensity of the reaction was variable in the three epididymal zones. Labeling was of low intensity in the proximal and middle caput, except in the granules of the latter. These granular storage sites did not correspond to typical secretory granules but appeared to be intracellular sites of degradation of this protein. In the distal caput, which was devoid of these granules, intense secretory activity for antagglutinin was detected. Few gold particles were localized in the RER profiles but labeling was detected in the Golgi zone, in numerous dense vesicles, in structures distributed between the Golgi zone and the apex of the cell, and in the epididymal lumen. This study has enabled us to visualize immunocytochemically antagglutinin along its intracellular secretory pathway, i.e. at the site of its synthesis, during its passage via the Golgi zone, and its intracellular transport to the lumen.     

Androgenic control of antagglutinin secretion in the boar epididymal epithelium

Summary Antagglutinin, a specific protein synthesized by the boar epididymis, was secreted by the principal cells of the initial segment, the caput and the corpus, but was not detectable in the caudal cells. Castration completely abolished the synthesis and secretion of antagglutinin in all epididymal cells. Androgen replacement suggests that the epithelial cells from different segments have differential regulatory mechanisms. The proximal zone appeared refractory to exogenous testosterone; the median zone was a typical androgen-dependent region; and the caudal cells, where an unusual secretion of antagglutinin was detected, revealed still a different reaction pattern. It is postulated that these latter cells depend not solely on androgen but also or exclusively on other factors. Our results, which demonstrate a primary role of the Golgi complex in the secretory process in the epididymal cells, also suggest that the apical smooth endoplasmic reticulum may be implicated in the intracellular transport of glycoproteins to the cell surface.     

Immunocytochemical localization of antagglutinin in the boar epididymis

Summary Antagglutinin, a specific protein synthesized by the boar epididymis, was localized by the biotin-streptavidin method in all the principal cells of the caput and corpus epididymidis as well as in the lumen of this organ. Intracellular staining, which was first detected in the initial segment, appeared stronger in the distal caput and in the corpus but diminished and disappeared in the caudal epididymal cells. In all the principal cells, a consistent reaction product was localized in the large Golgi complex. Only slight and diffuse immunoreactive material was detected in the cytoplasm, except in the middle caput where the heterogeneous reactive granules appeared to be intracellular sites of degradation of this protein. In the lumen, the intensity of reaction increased from the caput to the cauda. Antagglutinin appeared strongly associated with the luminal surfaces, especially around and between the stereocilia. However, the spermatozoa also exhibited a distinct pattern of immunostaining. The results are discussed in relation to protein secretion in the epididymis and to the role of antagglutinin in the gamete-interaction process.