Natriumgradient

Natriumgradient, or the sodium gradient, refers to the difference in sodium ion (Na+) concentration across a cellular membrane along with the electrical potential carried by Na+. It constitutes an electrochemical potential that can drive the movement of Na+ and power a variety of transport processes across membranes.

The gradient is established and maintained primarily by the Na+/K+-ATPase, which uses cellular energy to pump Na+ out of the cell and K+ into the cell. This active transport creates high Na+ concentrations outside the cell and relatively low concentrations inside, contributing to a negative resting membrane potential in many cells. Typical extracellular Na+ is about 140 mM, while intracellular Na+ is around 5–15 mM, though values vary by tissue. The resulting electrochemical driving force for Na+ is a central factor in cellular excitability and transport phenomena.

Physiological roles include the initiation and propagation of action potentials in neurons, where Na+ influx follows the gradient during depolarization. In epithelial tissues such as the kidney and intestine, the Na+ gradient powers secondary active transport systems that reabsorb nutrients and water, exemplified by Na+-glucose cotransport and Na+/H+ exchangers. It also underpins secondary exchange mechanisms like Na+/Ca2+ exchange in calcium homeostasis.

Measurement and dynamics of the natriumgradient can be studied using electrophysiological techniques and ion-selective methods, with changes in the gradient reflecting cellular activity, ischemia, or disease states.