Glycoproteins and glycolipids of rat small intestinal microvillus and basolateral membranes.

Abstract

Glycoprotein and glycolipid constituents were examined in purified microvillus and basolateral membranes isolated from rat small intestinal epithelial cells. SDS-polyacrylamide gel electrophoresis showed that the molecular weights of most of the major proteins from microvillus membranes were over 100 kD, whereas the majority of those from basolateral membranes tended to have lower molecular weights. Glycoprotein profiles were also examined using three labeling methods, and in each case marked differences were observed between microvillus and basolateral membranes. In both membranes, lectins with a specificity toward N-linked sugar chains bound to the majority of the glycoproteins, in contrast to those lectins which preferentially bind to O-linked sugar chains. Glycolipids were labeled in vivo and isolated from both membrane fractions. Some differences were observed in the fucolipids and neutral glycolipids suggesting a more complex pattern in microvillus membranes. These results indicate that there are differences in the glycoprotein and glycolipid compositions of microvillus and basolateral membranes that may reflect the functional polarity of intestinal epithelial cells.