Effects of intracellular pH on calcium‐activated potassium channels in rabbit tracheal smooth muscle.

Abstract

SUMMARY1. The effects of intracellular pH (pHi) on calcium-activated potassium channels (Ca2+-activated K+ channels) were studied in membrane patches of smooth muscle freshly dispersed from the rabbit trachea. Single-channel currents were recorded with an 'inside-out' patch clamp technique, mainly at 0 mV, with the external (electrode) medium containing 130 mM-K+ and the internal (bath) medium 6 mM-K+.2. With an internal Ca2+ concentration ([Ca2+]

Modulation of the Ca2+-Activated Large Conductance K+ Channel by Intracellular pH in Human Renal Proximal Tubule Cells.

“…Furthermore, we attempted to explore the mechanism of pH i -sensitivity of this BK channel with kinetic analysis and to characterize the pH i -mediated channel gating. It had been shown in some reports that lowering pH i reduced the conductance of BK channels and that raising pH i enhanced it besides the pH i effect on channel activity [9,15,20]. However, changes in pH i induced no significant effect on the conductance of the BK channels in RPTECs (Fig.…”

“…The effect of changes in pH i on the Ca 2ϩ -sensitivity of BK channels was reported in various tissues [14][15][16][17][18]21]. Regarding this mechanism, several investigators have proposed that Ca 2ϩ and H ϩ could compete for binding to the Ca 2ϩ -binding sites [14][15][16]18].…”

“…Regarding this mechanism, several investigators have proposed that Ca 2ϩ and H ϩ could compete for binding to the Ca 2ϩ -binding sites [14][15][16]18]. [17].…”

“…Besides Ca 2ϩ and voltage, other factors such as ATP [8-11], pH [8, 9, 12-21], and Mg 2ϩ [19,[22][23][24] were also reported to modulate BK channels. Among these factors, intracellular pH (pH i ) is one of the significant factors that affect channel activity [8,9,[12][13][14][15][16][17][18][19][20][21], i.e., channel activity is inhibited by intracellular acidification and stimulated by its alkalization. Although the mechanism for pH i effects on channel activity was not precisely understood, two different mechanisms have been proposed.…”

“…One is that an increased cytoplasmic H ϩ can compete with Ca 2ϩ in binding to the same sites, thereby inhibiting channel activity [14][15][16], whereas the other is that the pH i -mediated change in channel activity is not competitive with Ca 2ϩ [17]. Moreover, it was demonstrated that the conductance of some BK channels was reduced by lowering pH i and enhanced by raising it [9,15,20].In the renal tubules, BK channels have been reported in cultured rabbit proximal tubule cells [25] …”