Structural correlates of glutaraldehyde induced uncoupling in mouse liver gap junctions.

The structure of gap junctions in unfixed and glutaraldehyde fixed rapid-frozen mouse liver has been examined in the rotary shadowed freeze-fracture replicas. Glutaraldehyde fixation alters the packing of connexons and reduces the average interconnexon spacing from 10.2 +/- 2.4 nm in unfixed preparations to 8.7 +/- 1.9 nm in the fixed preparations. The fixed, glycerinated and conventionally frozen preparations display an average interconnexon spacing of 8.8 +/- 1.6 nm. In the light of well-known cross-linking and denaturing properties of glutaraldehyde it has been suggested that fixation perhaps results in conformational alterations in the connexons leading to slight contraction of the gap junctional lattice of connexons. Based upon these results, the structural correlates of glutaraldehyde induced uncoupling are presumably different from the ones induced by functional uncouplers such as the free cytoplasmic concentrations of Ca2+ and/or H+ ions, which obliterate the low resistance channels in the connexons.