Relationships between intramembranous particles and surface coat carbohydrates in cells of a compact tissue.

The structural relationships between intramembranous particles (IMPs) and surface carbohydrates have been studied in cells of a compact tissue--uterine epithelial cells--using an in vivo technique. This involves introducing small amounts of glycerol into the uterine lumen of anaesthetized rats. The treatment results in extensive aggregation of IMPs in the apical plasma membrane of the epithelial cells, but no change in the distribution of several surface carbohydrates could be detected. Our findings indicate that, in this case, the carbohydrates are not the surface expression of the IMPs, which are generally believed to represent integral membrane proteins. We suggest that the structural relationships between IMPs and surface carbohydrates in the plasma membrane of this compact tissue cell are more similar to those in membranes of free-floating nucleated cells than to those in the much-studied erythrocyte membrane.