Multiple conductance states of newly formed single gap junction channels between insect cells.

Two cells of an insect cell line (Aedes albopictus, clone C6/36) were pushed together to form a cell pair while the intercellular current flow was monitored. This approach enabled us to study the formation of gap junction channels and explore their electrical properties. We found that the single channels exhibit multiple conductance states. The conductance of a fully open channel was 365 pS; the subconductance steps were 1/7 to 1/5 of the maximal conductance. The voltage gradient across the junction did not influence the conductance of fully open channels, but affected the dwell time at particular conductance states. The latter provides an explanation for the voltage-dependent conductance of gap junction membranes seen in these cells. The very first channel opening always was slow (15-50 ms), suggesting the involvement of a mechanism different from conventional channel gating.