Fig. 3.

Reabsorption of glucose in the proximal tubule. (a) Epithelial cells of the S1 and S2 segments of the proximal tubule express SGLT2 on the apical membrane and GLUT2 on the basolateral membrane. (b) Epithelial cells of the S3 segment express SGLT1 on the apical membrane and GLUT2 on the basolateral membrane. In both S1/S2 and S3 segments, glucose reabsorption occurs, first via glucose transport across the apical membrane by SGLTs and then by passive glucose exit towards the plasma via GLUT2. The sodium gradient across the apical membrane is maintained by the basolateral Na⁺/K⁺ pump. At an extracellular NaCl concentration of 150 mmol/l, a membrane potential of −50 mV and at 37°C, the human SGLT2 has a K_m for glucose of 5 mmol/l, a K_i for phlorizin of 11 nmol/l and a sodium:glucose coupling ratio of 1:1. Under the same conditions, human SGLT1 has a glucose K_m of 2 mmol/l, a phlorizin K_i of 140 nmol/l, and a sodium:glucose coupling ratio of 2:1. Adapted from [6], distributed under the terms of the CC BY 4.0 Attribution License (http://creativecommons.org/licenses/by/4.0/). This figure is available as part of a downloadable slideset