Morphometric analysis of gap junctions in rat myocardium after hyperkalemia.
The effect of membrane depolarization was investigated on gap junctions from isolated rat hearts perfused with a modified Krebs-Henseleit solution containing 16 mM K+. After freeze-fracturing, the configuration of the junctional particles in the ventricular myocardium was analysed by measurements of connexon densities and centre-to-centre distances between neighbouring particles. Both in control and hyperkalemic tissue, the gap junctions occur on the intercalated discs as round or oval aggregates of connexons which are closely and regularly packed in small, criss-cross-oriented arrays separated by particle-free aisles. Within the arrays, the mean (+/- SD) centre-to-centre distances between particles from control and hyperkalemic tissue, i.e. 9.17 +/- 1.52 and 9.15 +/- 1.51 mm, respectively, are not significantly different. Similarly, comparison of particle densities after control and high-K+ perfusion, i.e. 8,490 +/- 600 and 8,420 +/- 620 particles/microns 2, respectively, reveals no difference in the proportion of the particle arrays to the empty aisles. The apparently unaltered gap junctional morphology after depolarization of the sarcolemma by high-K+ perfusion provides support for the electrophysiological finding that the conductance of cardiac gap junctions is insensitive to membrane potential.
Scheuermann
D W
DW
Institute of Histology and Microscopic Anatomy, University of Antwerp, Belgium.
De Mazière
A M
AM
Aertgeerts
P A
PA
D000818:Animals; D005614:Freeze Fracturing; D006947:Hyperkalemia / Q000473:pathology*; D066298:In Vitro Techniques; D007365:Intercellular Junctions / Q000648:ultrastructure*; D008297:Male; D009206:Myocardium / Q000473:pathology*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values