Gap junction dynamics: reversible effects of divalent cations.

Abstract

Reversible changes in gap junction structure similar to those previously seen to parallel electrical uncoupling are produced by treating with Ca2 or Mg2 gap junctions isolated in EDTA from calf lens fibers. The changes, characterized primarily by a switch from disordered to crystalline particle packings, occur at a [Ca2] of 5 .cntdot. 10-7 M or higher and a [Mg2+] of 1 .cntdot. 10-3 M or higher and can be reversed by exposing the junctions to Ca2 and Mg2+ -free EGTA [ethylene glycol bis (.beta. aminoethyl ether) tetracetate] solutions. Similar changes are obtained in junctions of rat stomach epithelia incubated at 37.degree. C in well-oxygenated Tyrode''s solutions containing a Ca2 ionophore (A23187). Deep etching experiments on isolated lens junctions show that the true cytoplasmic surface of the junctions (PS face) is mostly bare, suggesting that the particles may not be connected to cytoskeletal elements. A hypothesis is proposed suggesting a mechanism of particle aggregation and channel narrowing based on neutralization of negative charges by divalent cations or H+.