TY - JOUR
T1 - Effects of the external pH on Ca channels
T2 - Experimental studies and theoretical considerations using a two-site, two-ion model
AU - Iijima, T.
AU - Ciani, S.
AU - Hagiwara, S.
PY - 1986
Y1 - 1986
N2 - Some effects of the external pH on Ca channels were studied in a hybridoma cell line (mAb-7B), by using the whole-cell configuration of the patch-clamp technique. As the pH was lowered, both the activation and the inactivation curves shifted toward less negative membrane potentials, suggesting a pH-induced decrease of an external negative surface potential, sensed by the mechanism of gating. The potential for half-activation, V( 1/2 ), and that for half-inactivation V(h), were related by a straight line with a slope of one. The inward current varied exponentially with V( 1/2 ), as would be expected if the field inside the channel and the Ca2+ concentration at the entrance were sensitive to the surface potential. However, the reversal potential and the outward current were unaltered by changes in the pH. Under the hypothesis that the channel senses the surface potential, all these results, as well as the nernstian behavior of the reversal potential with respect to Ca2+, observed in previous studies, are accounted for by a three-barrier, two-ion model for a channel, provided it is assumed that the potential in the channel drops almost entirely across the barrier adjacent to the external solution.
AB - Some effects of the external pH on Ca channels were studied in a hybridoma cell line (mAb-7B), by using the whole-cell configuration of the patch-clamp technique. As the pH was lowered, both the activation and the inactivation curves shifted toward less negative membrane potentials, suggesting a pH-induced decrease of an external negative surface potential, sensed by the mechanism of gating. The potential for half-activation, V( 1/2 ), and that for half-inactivation V(h), were related by a straight line with a slope of one. The inward current varied exponentially with V( 1/2 ), as would be expected if the field inside the channel and the Ca2+ concentration at the entrance were sensitive to the surface potential. However, the reversal potential and the outward current were unaltered by changes in the pH. Under the hypothesis that the channel senses the surface potential, all these results, as well as the nernstian behavior of the reversal potential with respect to Ca2+, observed in previous studies, are accounted for by a three-barrier, two-ion model for a channel, provided it is assumed that the potential in the channel drops almost entirely across the barrier adjacent to the external solution.
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U2 - 10.1073/pnas.83.3.654
DO - 10.1073/pnas.83.3.654
M3 - Article
C2 - 2418439
AN - SCOPUS:0010229838
VL - 83
SP - 654
EP - 658
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 3
ER -