This study was conducted to assess the effects of chemical carcinogens
on the gap junction-mediated intercellular communication in cultured
mammalian cells. The method of scrape-loading dye transfer of lucifer
yellow was adapted as a measure of gap junctional communication. Clone
9 cells derived from rat liver were treated with a model chemical car
cinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and the gap junct
ional communication was assessed by measuring the transfer of scrape-l
oaded lucifer yellow dye. When cells were treated with the carcinogen
at 0.3 mg/ml, the fluorescent dye transfer was inhibited by 90% in 60
min. Other chemical agents, which include direct or indirect carcinoge
ns and antitumor drugs, were also examined for their effects on the ga
p junctional communication. Direct carcinogens, such as MNNG, hydroxyl
amine and ethidium bromide, exhibited strong inhibition of intercellul
ar communication, while indirect carcinogens, such as aflatoxin B-1 an
d ethionine, exerted minor effects. Effects of test chemicals on the c
ell communication through gap junctions were readily quantitated by co
unting the number of cells stained with the fluorescent dye.