Modifications of sodium channel gating in Myxicola giant axons by deuterium oxide, temperature, and internal cations

Journal Article · Wed Aug 01 00:00:00 EDT 1979 · Biophys. J.; (United States)

DOI:https://doi.org/10.1016/S0006-3495(79)85211-X· OSTI ID:5658762

Schauf, C L; Bullock, J O

In dialyzed Myxicola axons substitution of heavy water (D/sub 2/O) externally and internally slows both sodium and potassium kinetics and decreases the maximum conductances. Furthermore, this effect is strongly temperature dependent, the magnitude of the slowing produced by D/sub 2/O substitution decreasing with increasing temperature over the range 3 to 14/sup 0/C with a Q/sub 10/ of approx. 0.71. The relatively small magnitude of the D/sub 2/O effect, combined with its strong temperature dependence, suggests that the rate limiting process producing a conducting channel involves appreciable local changes in solvent structure. Maximum conductances in the presence of D/sub 2/O were decreased by approx. 30%, while the voltage dependences of both g/sub Na/ and g/sub K/ were not appreciably changed. In contrast to the effects of heavy water substitution on the ionic currents, membrane asymmetry currents were not altered by D/sub 2/O, suggesting that gating charge movement may precede by several steps the final transformation of the Na/sup +/ channel to a conducting state. In Myxicola axons the effect of temperature alone on asymmetry current kinetics can be well described via a simple temporal expansion equivalent to a Q/sub 10/ of 2.2, which is somewhat less than the Q/sub 10/ of G/sub Na/ activation. The integral of membrane asymmetry current, representing maximum charge movement, is however not appreciably altered by temperature.

• Research Organization: Rush Univ., Chicago, IL
• OSTI ID: 5658762
• Journal Information: Biophys. J.; (United States), Vol. 27:2
• Country of Publication: United States
• Language: English

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