Gap junction connexon configuration in rapidly frozen myocardium and isolated intercalated disks.

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Abstract
By using 2 ultrarapid freezing techniques, the structure of rat and rabbit cardiac gap junctions was captured in a condition closer to that existing in vivo than to that previously achieved. The junctions characteristically consist of multiple small hexagonal arrays of connections. In tissue frozen 10 min after animal death, however, unordered arrays are common. Examination of junction structure at intervals up to 40 min after death reveals a variety of configurations including dispersed and close-packed unordered arrays, and hexagonal arrays. By use of an isolated intercalated disk preparation, the configuration of cardiac gap junctions in vitro was shown to be unalterable by factors normally considered to induce functional uncoupling. These experiments demonstrate that, contrary to the conclusions of some earlier studies, the arrangement of gap junction connections, in cardiac tissue at least, cannot be used as a reliable guide to the functional state of the junctions.