Ultrastructural localization of keratin and alpha-L-fucose in human eccrine sweat glands.

Human eccrine sweat glands were embedded in Lowicryl K4M. Cytokeratin proteins and blood group H antigen were localized by applying a postembedding immunogold method using a monoclonal antikeratin antibody and the lectin Ulex europaeus I. The antikeratin antibody labeled intermediate filaments in the secretory coil and dermal duct. Within dark secretory cells bundles of filaments criss-crossing the cell were labeled. Within the luminal cells of the dermal duct filaments arranged parallel to the cell surface and lying in the apex of the cell were labeled, too. The association of keratin filaments with desmosomes was visualized demonstrating their subcellular connection with other cell organelles. The desmosomes themselves remained unlabeled. The lectin Ulex europaeus I is a blood group H specific lectin and binds to alpha-L-fucosyl-containing glycoproteins. Dark cells of the secretory coil reacted with the lectin. Here the secretory granules, the lateral cell membranes, and the microvilli membranes were labeled. The endoplasmatic reticulum, the Golgi complex, and transport vesicles were not labeled, although the glycoprotein synthesis is considered to be located in the Golgi complex. Thus, either the number of alpha-L-fucose molecules in the Golgi is too low to be detected by the technique employed or the determinant of blood group H antigen is released after the secretory granules and transport vesicles leave the Golgi complex.