A Scanning Electron Microscopic Study on the Fractured Rat Parietal Cells in Resting State and after Stimulation with Tetragastrin

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Abstract
Parietal cells in the rat gastric mucosa fractured by freeze cracking methods under resting (control) state and tetragastrin stimulation were studied by field emission scanning electron microscopy. The structures thus revealed were compared with those studied by transmission electron microscopy. In the fractured cytoplasm, intracellular canaliculi lined by numerous microvilli invaginated deeply towards the basal cytoplasm. Tubulo-vesicles appeared as many small holes of about 0.05 .mu. in diameter and were distributed predominantly in the apical or pericanalicular cytoplasm. Some tubulo-vesicles directly opened into the secretory canaliculi. Occasionally, tiny microvilli appeared in tubulovesicles. After being stimulated for 30 min with tetragastrin, the secretory canaliculi of parietal cells became enlarged and there was a concomitant increase in both the number and size of microvilli. Tubulo-vesicles also were increased in size and number and the tiny microvilli in them were also increased. The tubulo-vesicles were enlarged presumably as a result of membrane fusion between contiguous tubulo-vesicles. The enlargement of the secretory canaliculi was the result of fusion of the membrane of a single tubulo-vesicles or a confluence of tubulo-vesicles to that of the secretory canaliculus and the successive disappearance of the fused membrane.