Action of extracellular pH on Na+ and K+ membrane currents in the giant axon ofLoligo Vulgaris

Carbone, Emilio; Fioravanti, R.; Prestipino, Gianfranco; Wanke, Enzo

doi:10.1007/bf01871693

Cited by 51 publications

(30 citation statements)

References 32 publications

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“…The effects of pH o on K v currents in pulmonary arterial smooth muscle cells are qualitatively similar to those observed for delayed rectifier K + channels in other preparations including squid giant axon [10,18] and frog node of Ranvier [11]. The effects of elevated pH o we observed were due primarily to an increase ing K, , whereas low pH o caused a positive shift in the voltage dependence of K + current activation and reducedg K .…”

Section: Discussionsupporting

confidence: 75%

pH regulation of voltage-dependent K + channels in canine pulmonary arterial smooth muscle cells

Ahn

Hume

1997

Pfl�gers Archiv European Journal of Physiology

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Voltage-dependent K+ currents (Kv) may play a role in hypoxic pulmonary vaso constriction. The effects of changes in extracellular pH (pHo) and intracellular pH (pHi) on Kv currents in smooth muscle cells isolated from canine pulmonary artery were studied using the amphotericin B perforated-patch technique for whole-cell recording. Under these conditions, cellular mechanisms for pHi regulation remain intact, and the effects of pHo were examined by directly changing the pH of external solutions and changes in pHi were produced by external application of weak extracellular acids and bases and the cation/H+ ionophore, nigericin. Ca(2+)-free external solutions were used to isolate whole-cell Kv currents from contaminating Ca(2+)-activated K+ currents. Extracellular acidification (pHo = 6.4-7.0) reduced Kv currents, produced a positive voltage shift in steady-state activation and reduced maximum Kv conductance (gK). Extracellular alkalinization (pHo = 8.0-8.4) increased Kv currents, produced a small negative voltage shift in steady-state activation, and increased gK. Intracellular acidification produced by exposure of cells to external sodium butyrate (20 mM) or nigericin (5 micrograms/ml) increased Kv currents, produced a negative voltage shift in steady-state activation, and increased gK. Intracellular alkalinization produced by exposure of cells to external trimethylamine (20 mM) reduced Kv currents, produced a small positive voltage shift in steady-state activation and reduced gK. These results suggest that the effects of pHo and pHi on Kv currents are distinctly different, but are consistent with reported effects of pHo and pHi on hypoxic pulmonary vasoconstriction, suggesting that such modulation may be mediated in party by pH-induced alterations in Kv channel activity.

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Section: Discussionsupporting

confidence: 75%

pH regulation of voltage-dependent K + channels in canine pulmonary arterial smooth muscle cells

Ahn

Hume

1997

Pfl�gers Archiv European Journal of Physiology

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“…Moreover, the voltage-dependent properties of the sodium conductance did not change appreciably at the lower pH (Schauf & Davis, 1976). Similar experiments using axons from LoIigo and Rana were interpreted as titration of surface charges not directly related to the gating mechanism (Hille, 1968;Carbone et al, 1978). The potassium channels in Myxicola axons experienced a shift in V 9 but no change in n when the pH was lowered (Schauf & Davis, 1976).…”

Section: Discussionmentioning

confidence: 56%

Evidence for titratable gating charges controlling the voltage dependence of the outer mitochondrial membrane channel, VDAC

1985

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A voltage-dependent anion-selective channel, VDAC, is found in outer mitochondrial membranes. VDAC's conductance is known to decrease as the transmembrane voltage is increased in either the positive or negative direction. Charged groups on the channel may be responsible for this voltage dependence by allowing the channel to respond to an applied electric field. If so, then neutralization of these charges would eliminate the voltage dependence. Channels in planar lipid bilayers which behaved normally at pH 6 lost much of their voltage dependence at high pH. Raising the pH reduced the steepness of the voltage dependence and raised the voltage needed to close half the channels. In contrast, the energy difference between the open and closed state in the absence of a field was changed very little by the elevated pH. The groups being titrated had an apparent pK of 10.6. From the pK and chemical modification, lysine epsilon amino groups are the most likely candidates responsible for VDAC's ability to respond to an applied electric field.

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“…The fixed charge surface density obtained in our experiments is lower than the available data for animal cell membranes. The differences between H + and Ca 2+ binding constant are still greater (Begenisich, 1975;Drouin, 1976;Carbone et al, 1978). This suggests that the nature of groups carrying negative fixed charges on the Nitella cell plasmalemma is different from similar groups on the animal cell membranes.…”

Section: Plasmalemma Surface Charges and Their Effects On K+-channel mentioning

confidence: 84%

Potassium channels in plasmalemma ofNitella cells at rest

Соколик¹,

Yurin²

1986

J. Membrain Biol.

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Summary. Cation channels of passive transport in the plasmalemma of Nitella flexilis cells at rest were studied by the voltageclamp technique using microelectrodes. Two types of potassium channels have been identified. They are activated at different voltages: over -100 to -80 mV (D-channels) and below -100 mV (H-channels). The zero-current potential of instantaneous voltage-current curves (IVCC's) for both types of channels shifts by 50 to 55 mV in response to a 10-fold increase of K + concentration in the solution. Ion movement in D-channels follows the free diffusion mechanism; in H-channels the independence principle is violated. The channel selectivity (in the order of decreasing permeability) is: K + > Rb + > NH~ > Na + > Li + > Cs + > TEA + choline*. It has been found that D-channel Cs + block is potential dependent while tetraethylammonium (TEA +) blocks Hchannels in a potential-independent manner, but H + ions do not affect the inward potassium current of the channels. Two types of potassium channels appear to be located in different parts of the membrane and their entrance parts are of different structure.

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Action of extracellular pH on Na+ and K+ membrane currents in the giant axon ofLoligo Vulgaris

Cited by 51 publications

References 32 publications

pH regulation of voltage-dependent K + channels in canine pulmonary arterial smooth muscle cells

pH regulation of voltage-dependent K + channels in canine pulmonary arterial smooth muscle cells

Evidence for titratable gating charges controlling the voltage dependence of the outer mitochondrial membrane channel, VDAC

Potassium channels in plasmalemma ofNitella cells at rest

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