MOLECULAR ANATOMY OF AN ENDODERMAL GLAND - INVESTIGATIONS ON MUCUS GLYCOPROTEINS AND CELL TURNOVER IN BRUNNERS GLANDS OF DIDELPHIS-VIRGINIANA USING LECTINS AND PCNA IMMUNOREACTIVITY

Brunner's glands are located in the submucosa of the proximal duodenum and are unique to mammalian species. The North American opossum (Dide lphis virginiana) is generally regarded as a prototype marsupial that closely resembles fossil didelphids which can be placed at the beginni ng of mammalian evolution. The current investigation provided an oppor tunity for the analysis of secretory products from these glands in a s pecies thought to be more closely related to earlier evolutionary form s. Extracts of Brunner's glands were subjected to SDS-PAGE and Western blotting. The results indicate the presence of two high molecular wei ght PAS-positive glycoprotein bands. In addition to these two PAS-posi tive bands, several other glycoprotein bands were detected in the high molecular weight range that bind several lectins which typically reco gnize O-linked carbohydrates indicative of mucus type glycoproteins. T he same lectins bind to glandular structures in tissue sections. Compa rison of lectin binding sites with the pyloric glands of the stomach a nd duodenal goblet cells indicates that Brunner's glands carbohydrate residues resemble those of the pyloric glands more closely than those of the duodenal goblet cells. The low cell turnover rate in Brunner's glands is in contrast to the rapid turnover rate of goblet cell precur sors in the duodenal crypts. The mucus composition and the cell turnov er rate correlate well with embryological data and suggest that Brunne r's glands of Didelphis evolved from an epithelium more closely associ ated with the stomach than that of the duodenum as the topography of t he gland would suggest. (C) 1995 Wiley-Liss, Inc.