Figure 1.

Illustration of the basic tenets of the osmotic model of solute-coupled fluid absorption. Solute enters and exits the cells through specific pathways; in this illustration Na-coupled entry mechanisms (e.g., SGLT1) and facilitated/equilibrating carrier exit mechanisms (e.g., GLUT2) plus the Na-K ATPase. Water follows through separate pathways driven by osmotic differences. These flows are shown taking place in two different cells for convenience. B.M., basement membrane; CAP., capillary.