[MS] Cellular mechanisms of gastric acid secretion

Morphologically speaking within parietal cells, upon stimulation, tubovesicles by the (apical/basolateral) cytoplasm, which contain (K+/H+ or K+/Na+ ATPase channels) will become incorporated into the (apical/basolateral) membrane
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Terms in this set (10)
1. stimulation of phospholipase C

2. IP2 is converted to IP3 & DAG

3. IP3 stimulates Ca++ release from stores

4. Ca++ activates calmodulin-dependent protein kinase

5. DAG activates protein kinase C

6. histamine's action on H2 receptors activates adenylate cyclase which increases cAMP production from ATP

7. cAMP-stimulated protein kinase A, Ca++ and protein kinase C change parietal cell function

8. events occur within cell that lead to acid secretion
- H+ ions derived from water

- open K+ channels allow K+ diffusion into the canaliculi, so the proton pump is stimulated to hydrolyse ATP to expel H+ to draw the K+ ion back into the cell

- Cl- ions can enter the canaliculi via Cl- channels

- the OH- left from the first step reacts with CO2 in the presence of carbonic anhydrase to produce bicarbonate

- the bicarbonate is exchanged for Cl- ions in the basal membrane, the movement of bicarbonate down the electrochemical gradient drives inward transport of the Cl- ions

- bicarbonate diffuses into the blood

- produces the alkaline tide phenomena
- due to its actions, K+ ions accumulate inside the cell and can move down the electrochem gradient through channels in the basolateral and canalicular membranes

- the Na+/H+ exchanger in the basolateral membrane moves Na+ into the cell, down the elctrochem gradient and expels H+

- the exchanger provides Na+ ions for the pump, allowing the K+ content of the cell to be maintained

- the expulsion of H+ leaves more hydroxide ions to be converted to bicarbonate

- the increased bicarbonate means more Cl- will be drawn into the cell when it is brought in as bicarbonate is expelled

- more Cl- leaves through the canalicular channel into the canaliculi, to produce HCl, which also creates an osmotic flow of water to produce the secretion