Immunocytochemical localization of beta 1,4 galactosyltransferase in epithelial cells from bovine tissues using monoclonal antibodies.

Post-embedding immunocytochemistry was employed to investigate the distribution of UDP-galactose:N-acetylglucosamine galactosyltransferase (beta 1,4-GT) in epithelial cells from various bovine organs. Several well characterized monoclonal antibodies previously demonstrated to recognize distinct polypeptide epitopes within the primary structure of beta 1,4-GT were applied to thin sections from tissues embedded in Lowicryl K4M, followed by the protein A-gold technique. Immunoreactivity was observed in the Golgi apparatus of epithelial cells from intestine, thymus and trachea. No immunoreactivity was observed in other intracellular structures, including rough endoplasmic reticulum, nuclear envelope and goblet cell mucus droplets. Within the Golgi apparatus, the staining was restricted to several cisternae in the trans region, with most portions of the trans-Golgi network appearing unlabelled. However, in thymic epithelial-reticular cells trans-Golgi network portions resembling classical GERL elements were stained by the antibodies. Thus, although immunoreactivity was subcompartmentalized within the Golgi apparatus in all epithelial cell types examined, the extent of staining within the trans-Golgi network was variable. Immunoreactivity was not detected at the plasma membrane (ecto-galactosyl-transferase), except in the case of a subpopulation of tracheal cells that resemble brush cells. These results suggest that in the epithelial cells examined, the subcompartmental distribution of beta 1,4-GT within the Golgi apparatus is maintained across different types of epithelial cell organization. Moreover, no evidence for a general epithelial cell ecto-galactosyltransferase could be discerned with these reagents.