Structure and function of rat parietal cells during treatment with omeprazole, SCH 28080, SCH 32651, or ranitidine

For 2 weeks four groups of adult female rats were given daily peroral doses of 400 mumols/kg of one of the following inhibitors of gastric acid secretion: omeprazole, SCH 28080, SCH 32651, or ranitidine; additional control rats were given vehicle only. Six rats in each group were killed 2 h after the last dose and another six in each group at 48 h. Samples of the gastric corpus wall were processed for light and electron microscopy. The maximal reduction of stimulated acid secretion in parallel gastric fistula rats was 100%, 90%, 40%, and 85%, respectively. Forty-eight hours after the last dose only SCH 28080 produced significant inhibition of acid secretion. 'Vacuolation' of parietal cells was occasionally observed in paraffin sections. Such 'vacuoles', which were not found in plastic sections, probably represent dilated secretory canaliculi. A small number of lucid parietal cells--presumably in the process of desquamation--were seen in all groups of rats; their proportion was significantly higher 2 h after the last dose of ranitidine, SCH 28080, or SCH 32651 than in the controls. Forty-eight hours after the last dose the proportion of such degenerating parietal cells was about the same in all groups.