Co-transport ratio and % of glucose reabsorption[2]
SGLT1
Located in the S3 segment of the proximal tubule.
Has a 2Na+:1Glucose co-transport ratio and is responsible for 2% of glucose reabsorption
SGLT2
Is predominately located in the S1 and S2 segments of the proximal tubule.
Has a 1Na+:1Glucose co-transport ratio and is responsible for 98% of glucose reabsorption.
Including SGLT1 and SGLT2, there are total seven members in the human protein family SLC5A, several of which may also be sodium-glucose transporters[3].
Functions
These proteins use the energy from a downhill sodium gradient 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.)