Regulation of gap junctional charge selectivity in cells coexpressing connexin 40 and connexin

sion of connexin 40 (Cx40) and Cx43 in cardiovascular tissues varies as a function of age, injury, and development with unknown conse-quences on the selectivity of junctional communication and its acute regulation. We investigated the PKC-dependent regulation of charge selectivity in junctions composed of Cx43, Cx40, or both by simul-taneous assessment of junctional permeance rate constants (Bdye) for dyes of similar size but opposite charge, N,N,N-trimethyl-2-[methyl-(7-nitro-2,1,3-benzoxadiol-4-yl)amino]ethanaminium (NBD-M-TMA; 1) and Alexa 350 (1). The ratio of dye rate constants (BNBD-M-TMA/BAlexa 350) indicated that Cx40 junctions are cation selec-tive (10.7 0.5), whereas Cx43 junction are nonselective (1.22 0.14). In coexpressing cells, a broad range of junctional selectivities was observed with mean cation selectivity increasing as the Cx40 to Cx43 expression ratio increased. PKC activation reduced or elimi-nated dye permeability of Cx43 junctions without altering their charg