The Na-K-Cl cotransporter (NKCC) is a transport protein that aids in the secondary active transport of sodium, potassium, and chloride into cells. In humans there are two isoforms of this membrane transport protein, NKCC1 and NKCC2, encoded by two different genes (SLC12A2 and SLC12A1 respectively). Two isoforms of the NKCC1/Slc12a2 gene result from keeping (isoform 1) or skipping (isoform 2) exon 21 in the final gene product. NKCC1 is widely distributed throughout the human body; it has important functions in organs that secrete fluids. It is found specifically in the kidney, where it extracts sodium, potassium, and chloride from the urine so they can be reabsorbed into the blood. Function NKCC proteins are membrane transport proteins that transport sodium (Na), potassium (K), and chloride (Cl) ions across the cell membrane. Because they move each solute in the same direction, they are considered symporters. They maintain electroneutrality by moving two positively charged solutes (sodium and potassium) alongside two parts of a negatively charged solute (chloride). Thus the stoichiometry of the transported solutes is 1Na:1K:2Cl. However, there is a notable exception in squid giant axon as the symporter in this special cell has a stoichiometry of 2Na:1K:3Cl, although electroneutrality is still maintained. NKCC1 NKCC1 is widely distributed throughout the body, especially in organs that secrete fluids, called exocrine glands. In cells of these organs, NKCC1 is commonly found in the basolateral membrane, the part of the cell membrane closest to the blood vessels. Its basolateral location gives NKCC1 the ability to transport sodium, potassium, and chloride from the blood into the cell. Other transporters assist in the movement of these solutes out of the cell through its apical surface. The end result is that solutes from the blood, particularly chloride, are secreted into the lumen of these exocrine glands, increasing the luminal concentration of solutes and causing water to be secreted by osmosis. In addition to exocrine glands, NKCC1 is necessary for establishing the potassium-rich endolymph that bathes part of the cochlea, an organ necessary for hearing. Inhibition of NKCC1, as with furosemide or other loop diuretics, can result in deafness. NKCC1 is also expressed in many regions of the brain during early development, but not in adulthood. This change in NKCC1 presence seems to be responsible for altering responses to the neurotransmitters GABA and glycine from excitatory to inhibitory, which was suggested to be important for early neuronal development. As long