Sodiumdependent

Sodium-dependent is a descriptor used in biology to refer to processes, proteins, or pathways that require a sodium ion (Na+) or rely on the sodium gradient across cell membranes. In physiology, sodium-dependent transport most commonly denotes secondary active transport, where the energy of Na+ moving down its electrochemical gradient drives the movement of another solute against its gradient.

This gradient is established by the Na+/K+-ATPase, which pumps Na+ out of cells and K+ in, using ATP. Because the gradient persists, transporters can couple solute uptake to Na+, via symporters (cotransporters) or exchangers, often with specific Na+:solute stoichiometries such as 1:1 or 2:1.

Examples include the SGLT family (SGLT1 and SGLT2) that cotransport glucose with Na+ in the intestinal epithelium and renal proximal tubule; sodium-dependent phosphate transporters (NaPi) in kidney and intestine; and several amino acid transporters that depend on Na+ (within various SLC families). Many neurotransmitter transporters likewise rely on the Na+ gradient, making them sodium-dependent in function.

Clinical relevance exists because many sodium-dependent transporters are drug targets. For instance, SGLT2 inhibitors are used to treat type 2 diabetes by reducing renal glucose reabsorption. Understanding sodium dependence is important in physiology and pharmacology, as it underpins secondary active transport and related regulatory mechanisms.

Note that the term can also refer to enzymes or channels that require Na+ for activity, though it is most commonly used in the context of membrane transport processes driven by the sodium gradient.