Regulation of the basolateral potassium conductance of theNecturus proximal tubule

Publisher Website
Google Scholar
Abstract
Two methods, the measurement of the response of the basolateral membrane potential (V bl) of proximal tubule cells ofNecturus to step changes in basolateral K+ concentration, and cellular cable analysis, were used to assess the changes in basolateral potassium conductance (G K) caused by a variety of maneuvers. The effects of some of these maneuvers on intracellular K+ activity (a K i ) were also evaluated using double-barreled ion-selective electrodes. Perfusion with 0mm K+ basolateral solution for 15 min followed by 45 min of 1mm K+ solution resulted in a fall in basolateral potassium (apparent) transference number (t K),V bl anda K i . Results of cable analysis showed that total basolateral resistance,R b , rose. The electrophysiological effects of additional manipulations, known to inhibit net sodium reabsorption across the proximal tubular epithelium ofNecturus, were also investigated. Ouabain caused a fall int K accompanied by large decreases ina K i andV bl. Lowering luminal sodium caused a fall int K and a small reduction inV bl. Selective reduction of peritubular sodium, a maneuver that has been shown to block sodium transport from lumen to peritubular fluid, also resulted in a significant decrease int K. These results suggest thatG K varies directly with rate of transport of the sodium pump, irrespective of the mechanism of change in pump turnover.