 Increased NKCC2 activity aids in water reabsorption in the collecting duct through aquaporin 2 channels by creating a hypo-osmotic filtrate.NKCC1 and NKCC2 are encoded by genes on the long arms of chromosomes 15 and 5, respectively.A loss of function mutation of NKCC2 produces Bartter syndrome, an autosomal recessive disorder characterized by hypokalemic metabolic alkalosis with normal to low blood pressure.