The effects of membrane stretch on Ca2+-activated (maxi) K+ channels were examined in the apical membrane of cultured medullary thick ascending limb (MTAL) cells. Using cell-attached patch-clamp technique, we found that negative pressure (-33 ± 5 cmH2O) applied to the patch membrane increased fractional open probability (NP(o)) from 0.3 ± 0.2 to 29.9 ± 7.6% (n = 12) in the presence of 1.8 mM Ca2+ in the pipette. The activity returned to control on releasing the negative pressure. Reduction of extracellular osmolality from 293.2 ± 1.6 to 219.8 ± 1.1 mosmol/kg also activated K+ channels (NP(o) = 43.8 ± 12.2%, n = 8) in cell-attached patches. Removal of Ca2+ from both pipette and bathing solution inhibited osmotic activation of K+ channels. K+ channels were shown to be Ca2+-activated K+ channels by their conductance (146 ± 7 pS, n = 5) and Ca2+ dependence. Our data suggest that membrane stretch caused by swelling or possibly by tubular flow enhances Ca2+ entry across the apical cell membrane of MTAL cells activating maxi K+ channels.
|Original language||English (US)|
|Journal||American Journal of Physiology - Renal Fluid and Electrolyte Physiology|
|Issue number||3 (26/3)|
|State||Published - 1989|
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