Conductive properties of the rabbit outer medullary collecting duct: inner stripe
Koeppen, B.M.
American Journal of Physiology 248(4 Pt 2): F500-F506
1985
ISSN/ISBN: 0002-9513 PMID: 3985156 Document Number: 247144
Segments of outer medullary collecting duct were dissected from the inner stripe of the rabbit kidney (OMCDi) and perfused in vitro. The conductive properties of the tubule epithelium and individual cell membranes were determined by means of cable analysis and intracellular voltage-recording microelectrodes. In 35 tubules the transepithelial voltage (VT) and resistance (RT) averaged 17.2 .+-. 1.4 mV, lumen positive and 58.6 .+-. 5.3 K.OMEGA. .cntdot. cm, respectively. The basolateral membrane voltage, (Vbl) was -29.2 .+-. 2.1 mV (n = 23). The apical cell membrane did not contain appreciable ion conductances, as evidenced by the high values of apical cell membrane fractional resistance (fRa = Ra/Ra + Ra), which approached uhity (0.99 .+-. 0.01; n = 23). Addition of amiloride or BaCl2 to the tubule lumen was without effect on the electrical characteristics of the cell, as was a 2-foldreduction in luminal [Cl-]. The conductive properties of the basolateral cell membrane were assessed with bath ion substitutions. A 2-fold reduction in bath [Cl-] depolarized Vbl by 14.7 .+-. 0.4 mV (theoretical, 17 mV), while a 10-fold increase in bath [K+] resulted in only a 0.9 .+-. 0.4 mV depolarization (theoretical, 61 mV). Substituting bath Na+ with tetramethylammonium (from 150 to 75 mM) was without effect. Reducing bath [HCO3-] from 25 to 5 mM (constant Pco2) resulted in a steady-state deploratization of Vbl of 8.4 .+-. 0.4 mV that could not be attributed to conductive HCO3- movement. The basolateral cell membrane is predomiantely Cl- selective. Taken together, the results of this study are consistent with the role of this segment in electrogenic H+ secretion.