Parietal cells tubulovesicles

In whole-body autoradiography studies in mice, the radiolabel originating from uC-labeled omeprazole was found to be confined to the gastric mucosa (Fig. 2.6). With a similar technique, and using both fight and electron microscopic evaluation, omeprazole was found to label only the tubulovesicles and secretory membranes of the parietal cell, which contain the H+, K+-ATPase [3]. Electrophoretic analyses of the proteins from such membranes, purified after systemic administration of... 

When the resting parietal cell is stimulated by acid secretagogues, the tubulovesicles are transformed into the secretory canaliculus. The parietal cell has the largest mitochondrial content of any mammalian cell (—34% of cell volume) and the ATP generated by this is mainly used for acid secretion. Hydrolysis of ATP results in a conformational change in the protein that mediates the electroneutral exchange of intracellular and extracellular K+. The pump is activated only when it is associated with a potassium chloride pathway in the canalicular membrane (Fig. 3.6). This allows potassium chloride efflux into the extra-cytoplasmic space and thus results in the secretion of HCl at the expense of ATP... 

Schematic representation of the resting (left side) and stimulated (right side) state of the parietal cell. Basolateral membrane contains three major receptor classes gastrin (G), acetylcholine (ACh), and histamine (H). Their actions are mediated by cAMP responses, Ca changes, or both. In addition, there are a number of ion transport pathways. In the stimulated state, the apical membrane acquires H", K -ATPase contained in the tubulovesicles (tv) as well as the property of K+ and CI conductance, both of which are essential in the secretion of HCl. A change in cytoskeletal arrangement is also associated with stimulation. CaM = calmodulin SC -secretory canaliculus mf = microfilaments. [Reproduced with permission from D. H. Malinowska and G. Sachs, Cellular mechanisms of acid secretion, Clin. Gastroenterol. 13, 322 (1984).]...

Gerbino, A. Hofer, A. M. Mckay, B. Lau, B. W. Soybel, D. I. Divalent cations regulate acidity within the lumen and tubulovesicle compartment of gastric parietal cells. Gastroenterology 2004,126, 182-195. 

Electron micrographs of a resting and stimulated parietal cell showing the conversion of the cytoplasmic tubulovesicles to the microvilli of the secretory canaliculus. 

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