BK channels in the kidney.
OBJECTIVE
Large, BK (calcium-activated potassium) channels are now regarded as relevant players in many aspects of renal physiology, including potassium secretion. This review will highlight recent discoveries regarding the function and localization of BK in the kidney.


RESULTS
Patch clamp electrophysiology has revealed BK in cultured podocytes, glomerular mesangial cells, and in several tubule segments including principal cells (connecting tubules/principal cells), and intercalated cells of connecting tubules and cortical collecting ducts. Flow-induced potassium secretion is mediated by BK in the distal nephron and may be partly the result of shear stress-induced increases in cell calcium concentrations. ROMK-/- and wild-type mice on a high potassium diet exhibit BK-mediated potassium secretion, and studies of BK-alpha-/- and BK-beta1-/- mice suggest that flow-induced potassium secretion is mediated by BK-alpha/beta1, which is specifically localized in the apical membrane of the connecting tubule of the mouse and connecting tubule plus initial cortical collecting duct of the rabbit.


CONCLUSIONS
BK channels, located in glomerular cells and in many nephron segments, especially mediate potassium secretion in the combined condition of potassium adaptation and high flow. Understanding the molecular makeup of BK in specific renal cells and the dietary and physiological conditions for their expression can yield improved potassium-sparing compounds.
Grimm
P Richard
PR
Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, Nebraska 68198-5850, USA.
Sansom
Steven C
SC
D000818:Animals; D002118:Calcium / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004594:Electrophysiology; D051528:Guanylate Kinases / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007678:Kidney Glomerulus / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism / Q000502:physiology*; D050527:Mesangial Cells / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000737:chemistry / Q000378:metabolism; D011817:Rabbits
D051036:Large-Conductance Calcium-Activated Potassium Channels; D051528:Guanylate Kinases; D006152:Cyclic GMP; D011188:Potassium; D002118:Calcium