Intracellular microelectrode characterization of the rabbit cortical collecting duct.
Cortical collecting ducts of the rabbit were perfused in vitro and the intracellular potential (Vbl) was measured with KCl-filled microelectrodes. The ratio of apical to basolateral membrane resistance (Ra/Rbl) was estimated from the voltage divider ratio using cable analysis. In control tubules Vbl averaged--84.0 +/- 2.5 mV and Ra/Rbl was 0.83 +/- 0.11. Pretreatment of the rabbits with mineralocorticoid caused Vbl to hyperpolarize to--105.8 +/- 3.1 mV and Ra/Rbl to decrease slightly to 0.62 +/- 0.10. A 10-fold increase of the luminal [K+] caused a 40.6 +/- 3.1 mV depolarization of Vbl in control tubules and a 33.0 +/- 4.2 mV depolarization in tubules from DOCA-pretreated rabbits. Concurrently, Ra/Rbl decreased in both groups, consistent with the existence of a conductive K+ channel at the apical cell membrane. This apical K+ channel was not sensitive to amiloride but was blocked by Ba2+. Conductive movement of Na+ across the apical membrane was also apparent in that Ra/Rbl increased with amiloride from 0.61 +/- 0.10 to 1.45 +/- 0.28. A 10-fold increase in the bath [K+] caused a 28.6 +/- 3.8 and a 49.4 +/- 4.4 mV depolarization of Vbl in tubules obtained from control and DOCA-pretreated rabbits, respectively. In both groups Ra/Rbl increased, suggesting that the basolateral cell membrane also contains a conductive K+ channel. Taken together the results support a model in which the transepithelial reabsorption of Na+ and the transepithelial secretion of K+ are driven by the Na+-K+-ATPase located in the basolateral cell membrane, with passive movement of these ions occurring through separate conductive pathways in the apical cell membrane.
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D017609:Barium Compounds; D002462:Cell Membrane / Q000502:physiology; D002712:Chlorides; D003900:Desoxycorticosterone / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007684:Kidney Tubules / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
D017609:Barium Compounds; D002712:Chlorides; D007473:Ion Channels; C024986:barium chloride; D001464:Barium; D003900:Desoxycorticosterone; D000584:Amiloride; D012964:Sodium; D011188:Potassium