Function
Firstly, the Na+/K+ ATPase pump on the basolateral membrane of the proximal tubule cell uses ATP to move 3 sodium outward into the blood, while bringing in 2 potassium. This creates a downhill sodium gradient inside the proximal tubule cell in comparison to both the blood and the tubule. The SGLT proteins use the energy from this downhill sodium gradient created by the ATPase pump to transport glucose across the apical membrane against an uphill glucose gradient. Therefore, these co-transporters are an example of secondary active transport. (The GLUT uniporters then transport the glucose across the basolateral membrane, into the peritubular capillaries.) Both SGLT1 and SGLT2 are known as symporters, since both sodium and glucose are transported in the same direction across the membrane.
Read more about this topic: Sodium-glucose Transport Proteins
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