The Journal of Cell Biology, Vol 67, 801-813, Copyright © 1975 by The Rockefeller University Press
Opaque deposits on gap junction membranes after glutaraldehyde-calcium fixation
WJ Larsen
When cloned hybrid cells (A/Bm-5) were grown to confluence and fixed in
glutaraldehyde-calcium, electron-opaque deposits were observed on the
cytoplasmic faces of plasma membrane. Deposits were most abundant at gap
junctions. Deposits were often precisely paired, cell-to-cell, across the
gap junctional membranes, and these paired deposits were frequently
equivalent in size. This relationship was most often observed on long
profiles of gap junctions, in contrast to the asymmetric distribution of
larger deposits commonly found on short junctional profiles. Deposits were
present with or without heavy metal staining but did not appear when
calcium was omitted from the fixative. Fixation at room temperature yielded
more and larger deposits than fixation at 0 degrees C. The significance of
these observations is discussed with regard to the possible binding of
calcium at fixed membrane sites or the precipitation of calcium by anions
produced by enzymes located at the gap junction.
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