The sodium–hydrogen antiporter or sodium–hydrogen exchanger is a membrane protein found in many cells, and especially in those of the nephron of the kidney. Specifically in the intercalary cells of the collecting duct and in the epithelial cells of the proximal convoluted tubule. The membrane pump is primarily responsible for maintaining the balance of pH. Angiotensin II upregulates this antiporter in the proximal convoluted tubule in order to promote Na+ reabsorption and H+ secretion.
Regarding Dopamine Receptor Signaling: The Na+/H+ exchangers are a family of integral membrane proteins that regulate intracellular pH and transcellular Na+ absorption. Heterologously expressed D2, D3, and D4 receptors  activate the widely expressed Na+/H+ exchanger NHE1.
There are several isoforms of the antiporter:
- Sodium–hydrogen antiporter 1
- Sodium–hydrogen antiporter 2
- Sodium–hydrogen antiporter 3
- Sodium–hydrogen antiporter 5
- Sodium–hydrogen antiporter 6
- Sodium–hydrogen antiporter 8
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