Effects of four inorganic lead compounds on the proliferation and junctional coupling of cultured REL liver cells

BACKGROUND: Chronic, low-level exposure to inorganic lead (Pb) has been involved in a number of human diseases, including tumors. In this study, the effect of four different inorganic Pb compounds (acetate, chloride, monoxide, and sulfate) was evaluated, in vitro, on liver-derived REL cells, known to be very sensitive to tumor promoters. METHODS: Cytotoxicity and effects on intercellular communication (GJIC) were evaluated, respectively, by cell- density/proliferation and dye-transfer assays. Pb concentration in the media solutions used for each treatment was quantified by atomic absorption spectroscopy-electrothermal atomization. RESULTS: Each of the Pb compounds we tested showed a typical dose- and time-related effect on REL cell proliferation, this effect not being related to the free metal concentration. Contrary to classical tumor promoters, none of the compounds significantly affected REL GJIC (1-hour treatment). CONCLUSIONS: Our results are indicative of specificity in the effects of the different Pb compounds. The mechanism(s) of their action need further investigations.