A stretch-activated K+ channel in the basolateral membrane ofXenopus kidney proximal tubule cells

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Abstract
The present study examined whether a basolateral potassium ion (K+) channel is activated by membrane-stretching in the cell-attached patch. A K+ channel of conductance of 27.5 pS was most commonly observed in the basolateral membrane ofXenopus kidney proximal tubule cells. Channel activity increased with hyperpolarizing membrane potentials [at more positive pipette potentials (V p)]. Open probability (P o) was 0.03, 0.13, and 0.21 atV p values of 0, 40, and 80 mV, respectively. Barium (0.1 mM) in the pipette reducedP o by 79% at aV p of 40 mV. Application of negative hydraulic pressure (−16 to −32 cm H2O) to the pipette markedly activated outward currents (fromP o=0.01 to 0.75) at aV p of −80 mV, but not inward currents at aV p of 80 mV. The size of the activated outward currents (from cell to pipette) did not change by replacing chloride with gluconate in the pipette. These results indicate that a stretch-activated K+ channel exists in the basolateral membrane of proximal tubule cells. It may play an important role as a K+ exit pathway when the cell membrane is stretched (for example, by cell swelling).