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The Journal of Membrane Biology

, Volume 93, Issue 1, pp 11–21 | Cite as

Quantitative gap junction alterations in mammalian heart cells quickly frozen or chemically fixed after electrical uncoupling

  • J. Délèze
  • J. C. Hervé
Articles

Summary

The gap junction morphology was quantified in freeze-fracture replicas prepared from rat auricles that had been either quickly frozen at 6 K or chemically fixed by glutaraldehyde, in a state of normal cell-to-cell conduction or in a state of electrical uncoupling. The general appearance of the gap junctions was similar after both preparative procedures. A quantitative analysis of three gap junctional dimensions provided the following measurements in the quickly frozen conducting auricles (mean±sd): (a) P-face particles' diameter 8.27±0.74 nm (n =5709), (b) P-face particles' center-to-center distance 10.78±2.12 nm (n=4800), and (c) E-face pits' distance 9.99±2.19 nm (n=1600). Corresponding values obtained from chemically fixed tissues were decreased by about 3% for the particle's diameter and about 5% for the particles' and pits' distances. Electrical uncoupling by the action of either 1 mM 2–4-dinitrophenol (DNP), or 3.5 mMn-Heptan-1-ol (heptanol), induced a decrease of the particle's diameter, which amounted to −0.69±0.01 nm (mean ±se) in the quickly frozen preparations and −0.71±0.01 nm in the chemically fixed ones. The particles' distance was decreased by −0.96±0.04 nm in the quickly frozen samples and by −0.90 ±0.03 nm in the chemically fixed ones and the E-face pits' distance was similarly reduced. All differences were statistically significant (P<0.001 for all dimensions). Electrical recoupling after the heptanol effect promoted a return of these gap junctional dimensions towards normal values, which was about 50% complete within 20 min. It is concluded that very similar morphological alterations of the gap junctional structure are induced in the mammalian heart by different treatments promoting electrical uncoupling and that these conformational changes appear independently of the preparative procedure. The suggestion that the observed decrease of the particles' diameter is genuinely related to the closing mechanism of the unit cell-to-cell channel set in thei centers is thus confirmed.

Key Words

mammalian heart cell-to-cell conduction cell-to-cell conduction block electrical uncoupling gap junction quantitative gap junction electron microscopy quick-freezing at 6K 

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Copyright information

© Springer-Verlag New York Inc. 1986

Authors and Affiliations

  • J. Délèze
    • 1
  • J. C. Hervé
    • 1
  1. 1.Physiologie Cellulaire, Unité Associée au CNRS no. 290Université de PoitiersPoitiersFrance

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