Studying Na and K channels in aldosterone-sensitive distal nephrons.

Aldosterone-sensitive distal nephron (ASDN) including the distal convoluted tubule (DCT), connecting tubule (CNT) and collecting duct (CD) plays an important role in the regulation of hormone-dependent Na reabsorption and dietary K-intake dependent K excretion. The major Na transporters in the ASDN are thiazide-sensitive Na-Cl cotransporter (NCC), epithelial Na channel (ENaC), pendrin/Na-dependent Cl-bicarbonate exchanger (NDCBE). Whereas major K channels in the ASDN are Kir4.1 and Kir5.1 in the basolateral membrane; and Kir1.1 (ROMK) and Ca activated big conductance K channel (BK) in the apical membrane. Although a variety of in vitro cell lines of the ASDN is available and these cell models have been employed for studying Na and K channels, the biophysical properties and the regulation of Na and K channels in vitro cell models may not be able to recapitulate those in vivo conditions. Thus, the studies performed in the native ASDN are essential for providing highly physiological relevant information and for understanding the Na and K transport in the ASDN. Here we provide a detailed methodology describing how to perform the electrophysiological measurement in the native DCT, CNT and cortical collecting duct (CCD).