FINE-STRUCTURAL AND MORPHOMETRIC STUDIES ON GASTRIC PARIETAL-CELLS OFPEPTIC-ULCER PATIENTS AFTER LONG-TERM TREATMENT WITH OMEPRAZOLE

Omeprazole, a substituted benzimidazole, is known to inhibit acid secr etion from parietal cells in gastric glands, and is widely utilized as a drug for peptic ulcer, To clarify the ultrastructural changes in pa rietal cells from long-term treatment with a therapeutic dose of omepr azole, biopsy specimens of the gastric mucosa obtained from peptic ulc er patients were morphometrically analyzed before and after omeprazole treatment. Before treatment with omeprazole, parietal cells in both t he stimulated and resting stages were observed; the stimulated cells p ossessed smaller amounts of tubulovesicles in the cytoplasm and numero us profiles of microvilli in the intracellular canaliculi, whereas the cells in the resting phase showed numerous profiles of tubulovesicles and poorly developed microvilli in the canaliculi, Eight weeks after the onset of omeprazole treatment, the amounts of both tubulovesicles in the cytoplasm and microvilli in the intracellular canaliculi drasti cally decreased. These decreases in the profiles of the membrane struc tures with a proton pump occurred concomitantly with a significant inc rease in autophagic vacuole/autolysosome-like structures. These result s suggest that the membrane structures with proton pump are not recycl ed between tubulovesicles and microvilli of intracellular canaliculi i n parietal cells after omepratole treatment, but may be sequestrated i nto autophagosomes and degraded by lysosomal enzymes.