Gap junctions: correlated electrophysiological recordings and ultrastructural analysis by fast freezing and freeze-fracturing

Abstract

The effect of glutardialdehyde on the dynamic organization of gap junctions cannot only be seen by electrophysiological measurements where the uncoupling of cells occurs within 3 min, but also by freeze fracturing the cells. Gap junctions from unfixed cells rapidly frozen by dipping into liquid propane appear polymorphic; loosely packed and clustered plaques are found, as well as tightly packed aggregates, which are mainly found in fixed preparations. Whether these different structures correspond with different functional states, or whether they depend on the local configuration of the contacting membranes is difficult to decide. The presented results, however, support the idea of active (coupling competent) gap junctions with loosely packed channels and nonactive (permanently closed) gap junctions where the channels are tightly packed.