H +

[H⁺],

symbol for hydrogen ion.

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H⁺,K⁺-ATPase

[ā·tē·pē′ās]

a membrane-bound enzyme occurring on the secretory surfaces of parietal cells that uses the energy derived from the hydrolysis of ATP to drive the exchange of ions across the cell membrane, secreting acid into the gastric lumen. Protons and chloride ions are pumped against gradients across the apical membranes of activated parietal cells into the gastric lumen in exchange for potassium ions. See also adenosine triphosphatase.