Water absorption in the gut

Water absorption in the gut is a fundamental physiological process primarily occurring in the small and large intestines to maintain systemic fluid and electrolyte homeostasis [1, 9]. This process is not a single molecular target but a coordinated biological function mediated by several transport proteins, including sodium-glucose cotransporter 1 (SGLT1), sodium-hydrogen exchanger 3 (NHE3), and multiple aquaporin isoforms such as AQP3, AQP4, and AQP8 [2, 3, 8]. The mechanism is largely driven by osmotic gradients created by the active transport of solutes like sodium and glucose into enterocytes, which pulls water passively through transcellular and paracellular pathways [7, 17, 18]. Dysregulation of this process is central to various gastrointestinal pathologies; impaired absorption or excessive secretion causes diarrhea and life-threatening dehydration, while excessive water removal contributes to constipation [4, 8, 12]. Pharmacological management involves modulating these underlying transporters—for instance, Oral Rehydration Salts (ORS) utilize SGLT1 to stimulate absorption, while recent research identifies the TRPM4 ion channel as a master switch for fluid flow targeted by certain laxatives [5, 10, 15]. Maintaining this balance is also critical for gut microbiota stability and mucosal immune function [4, 12, 19].

Other names

Intestinal water absorptionGastrointestinal fluid transportColonic water reabsorptionEnterocyte water transport

Modulation of net fluid movement by establishing or disrupting osmotic gradients through the activation or inhibition of electrolyte transporters (e.g., NHE3, SGLT1), water-selective channels (Aquaporins), and regulatory ion channels (e.g., TRPM4, CFTR).