ELECTROPHYSIOLOGICAL PROPERTIES OF CULTURED OUTER MEDULLARY COLLECTING DUCT CELLS

Whole cell patch-clamp techniques were used to characterize the electrophysiological properties of cells from the inner stripe portion of the rabbit outer medullary collecting duct (OMCD(i)) grown in primary culture. With pipette and bathing solutions mimicking intracellular and extracellular fluid, the resting membrane voltage was -30 to -40 mV. The whole cell conductance exhibited slight outward rectification, and at the resting membrane voltage the cell conductance averaged 2.58 +/- 0.49 nS (n = 17). The major conductive ion species was Cl-. The Cl- conductance was also found to have a significant permeability to HCO3- and was inhibited by the Cl--channel blockers diphenylamine carboxylic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. A small K+ conductance was also present, but no Na+ conductance was detected. Current generated by the H+-adenosinetriphosphatase (H+-ATPase) was quantitated. This current was dependent on the presence of ATP in the pipette. Dicyclohexylcarbodiimide, N-ethylmaleimide, and bafilomycin A1, inhibitors of the vacuolar H+-ATPase, also reduced this outward current in an ATP-dependent manner. The inhibitor-sensitive component of the outward current, a measure of the current generated by the H+-ATPase, was in the range of 35-100 pA/cell.