Collecting duct adaptation to potassium depletion.

Kidneys are the main effectors of the maintenance of potassium balance, under both normal and altered conditions of dietary potassium uptake. The collecting duct system plays a major role in this control of potassium homeostasis because most of the filtered potassium is reabsorbed between the glomerulus and the distal convoluted tubule: under normal physiological conditions or in response to potassium loading, collecting ducts adjust their rate of secretion of potassium into urine so as it matches the dietary daily intake, whereas in response to restriction of potassium ingestion, this secretion process is mostly curtailed, and a reabsorptive mechanism appears. In this short review, we analyzed the cellular and molecular mechanisms underlying transepithelial transport of potassium in the collecting duct and their adaptation in response to potassium depletion. A special emphasis is given on the axial and cellular heterogeneity of the collecting duct with regard to potassium transport and its adaptation. We also discuss the factors controlling duct hypertrophy and hyperplasia during potassium depletion and their possible relationship with the control of potassium conservation.