Long-chain n-alkanols and arachidonic acid interfere with the V _m-sensitive gating mechanism of gap junction channels

Abstract

 Experiments were carried out on preformed cell pairs and induced cell pairs of an insect cell line (mosquito Aedes albopictus, clone C6/36). The coupling conductance, g _j, was determined with the dual voltage-clamp method. Exposure of preformed cell pairs to lipophilic agents, such as long-chain n-alkanols (n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol) or arachidonic acid, provoked a decrease in g _j. Hyperpolarization of both cells led to a recovery of g _j. Systematic studies revealed that this phenomenon is caused by a shift of the sigmoidal relationship g _j(ss) = f(V _m) towards more negative values of V _m (where g _j(ss) = conductance at steady-state; V _m = membrane potential). The shift was dose dependent, it developed with time and was reversible. The longer the hydrocarbon chain of n-alkanols, the lower was the concentration required to produce a given shift. Besides shifting the function g _j(ss) = f(V _m), arachidonic acid decreased the maximal conductance, g _j(max). Single-channel records gained from induced cell pairs revealed that the lipophilic agents interfere with the V _m-sensitive slow channel gating mechanism. Application provoked slow current transitions (transition time: 5–40 ms) between an open state of the channel (i.e. main state or residual state) and the closed state; subsequently, fast channel transitions (transition time: < 2 ms) involving the main state and the residual state ceased completely. Hyperpolarization of V _m or washout of the lipophilic agents gave rise to the inverse sequence of events. The single-channel conductances γ _{j(main state)} and γ _{j(residual state)} were not affected by n-heptanol. We conclude that long-chain n-alkanols and arachidonic acid interact with the V _m-sensitive gating mechanism.