DIFFERENT MUCINS ARE PRODUCED BY THE SURFACE EPITHELIUM AND THE SUBMUCOSA IN HUMAN TRACHEA - IDENTIFICATION OF MUC5AC AS A MAJOR MUCIN FROMTHE GOBLET CELLS

Mucins were extracted from the epithelial surface and the submucosal t issue of human trachea in order to enrich glycoproteins from the goble t cells and the submucosal glands respectively. The macromolecules wer e purified using density-gradient centrifugation, and the presence of the MUC5AC mucin was investigated using an antiserum raised against a synthetic peptide based on the sequence of the MUC5AC apoprotein. Muci ns from the surface epithelium showed a higher reactivity with the ant iserum relative to carbohydrate than those from the submucosa, and ion -exchange HPLC of reduced subunits revealed the presence of two distin ct mucin populations in the samples. The predominant species from the surface epithelium was more acidic than the major population from the submucosa and showed a strong reactivity with the anti-MUC5AC antiseru m. In contrast, the major portion of the submucosal mucins were less a cidic and showed no MUC5AC reactivity, although a more acidic populati on did react with the antibody. Rate-zonal centrifugation showed that the MUC5AC mucin from the surface epithelium is smaller than the major submucosal mucin, and that both are composed of subunits. Immunolocal ization confirmed that the MUC5AC mucin from human trachea originates from the goblet cells and that this glycoprotein is not a major produc t of the submucosal glands.