Gap junction crystallization in lens fibers after an increase in cell calcium

Previous studies have shown that cell uncoupling is paralleled by an increase in tightness and crystallinity of gap junction particle arrays. Gap junction crystallinity is believed to be part of the uncoupling mechanism because it can be produced in gap junctions isolated from lens fibers on direct exposure to uncoupling agents such as divalent cations or hydrogen ions. Some doubts, however, have been raised on the capacity of lens fiber junctions to crystallize and uncouple in situ. The present study shows that the gap junctions of rat lens fibers indeed crystallize after a treatment that increases drastically the membrane permeability to ions. The treatment consists of a brief immersion of the lenses in liquid nitrogen, followed by incubation for several hours in Tyrode's solution at 37 degrees C. Immediately after liquid nitrogen treatment, the lenses start gaining sodium and calcium while losing potassium, and eventually become opaque. Addition of 10 mM EDTA to calcium and magnesium-free Tyrode's solutions inhibits particle crystallization and lens cataract, whereas low concentrations of EDTA (1 mM) are not effective. These findings, together with preliminary data on the capacity of lens fibers to heal over, indicate that the gap junctions of lens fibers are capable of crystallizing and uncoupling in situ.