Renal acid-base transport: old and new players.

Systemic acid-base homeostasis is the product of complex interactions between metabolism, regulated exhalation of CO2 by the lungs and acid or base excretion by the kidneys. The importance of renal acid-base transport has been highlighted by mutations identified in several proteins involved in this task in patients with inborn forms of renal tubular acidosis. The underlying mechanisms of disease have been further studied in genetically altered mouse models and cell culture. An interesting field of research has focused on the question how changes in metabolism or acid-base homeostasis are sensed and result in altered excretion of acid or bases by the kidney. Several hormonal pathways including aldosterone and endothelin were implicated, a novel subfamily of proton-sensing receptors has been identified, and signaling molecules described that are activated by changes in pH.