Ultrastructure of tight junctions in prostaglandin-exposed rat stomach.

The effect of intragastric misoprostol, a synthetic prostaglandin E1 methyl ester analog, on the morphology of rat stomach was studied by transmission and scanning electron microscopy. Adult male Sprague-Dawley rats received misoprostol at dose levels ranging from 50 to 1000 micrograms/kg body weight and were sacrificed after 30 min. At all dose levels, normal organelle ultrastructure was maintained in epithelial cells on the surface, within gastric pits, and lining the gastric glands. Quantitative freeze-fracture electron microscopy was used to examine the influence of misoprostol on epithelial-cell tight junctions, major structural components of the mucosal barrier. The numbers of intramembrane fibrils and the depths of the tight-junction complexes did not differ significantly between controls and animals exposed to 1000 micrograms/kg misoprostol (P greater than 0.05). Therefore, alterations in gastric epithelial tight-junction ultrastructure do not appear to account for the cytoprotective effect of misoprostol.