AJP - Cell Physiology, Vol 260, Issue 3 C513-C527, Copyright © 1991 by American Physiological Society
Distinctive gap junction channel types connect WB cells, a clonal cell line derived from rat liver
D. C. Spray, M. Chanson, A. P. Moreno, R. Dermietzel and P. Meda
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461.
Gap junctions, dye coupling, and junctional conductance were studied in a
cell line (WB) that is derived from rat liver and displays a phenotype
similar to "oval" cells. In freeze-fracture replicas, two distinctive
particle sizes were detected in gap junctional plaques. Immunocytochemical
studies indicated punctate staining at membrane appositions using
antibodies to connexin 43 and to a brain gap junction-associated antigen
(34 kDa). No staining was observed using antibodies prepared against rat
liver gap junction proteins (connexins 32 and 26). Pairs of WB cells were
electrically and dye coupled. Junctional conductance (gj) between cell
pairs averaged approximately 10 nS; occasionally, gj was low enough that
unitary junctional conductances (gamma j) could be detected. Using a
CsCl-containing electrode solution, distinctive gamma j values were
recorded: approximately 20-30 pS, approximately 80-90 pS, and the sum of
the other sizes. The largest gamma j events were apparently due to random
coincident openings or closures of the smaller channels. Several treatments
reduced gj. Frequency distributions of gamma j were unaltered by 2 mM
halothane or 3.5 heptanol, but the sizes of intermediate and largest events
were reduced slightly by 100 nM phorbol ester, and the relative frequency
of the largest events was increased by 10 microM glutaraldehyde. We
conclude that the distinctive gamma j values represent openings and
closures of two distinct types of gap junction channels rather than
substates of a single channel type; these unitary conductances may
correspond to the dual immunoreactivity and to the two particle sizes seen
in freeze fracture.
