Toxic effects of octylphenol on cultured rat and murine splenocytes

Alkylphenol polyethoxylates and alkylphenols, such as 4-tertoctylphenol (OP), are environmental contaminants. Because these compounds are toxic to aquatic animals, we studied the effects of OP on splenocytes removed from male Fischer 344 rats or male Balb/c mice and cultured in vitro. Cell viability was assessed by trypan blue exclusion after 5 or 27 hr of culture. Culture with 0.08% ETOH (vehicle) or any dose of OP did not alter total cell number or the percentage of viable cells after 5 hr. Culture of cells with two different alkylphenol polyethoxylates for 5 hr resulted in the loss of all cells. The percentages of viable rat or mouse cells after 27 hr of culture were decreased significantly by 10(-12) M OP or greater concentrations. The actions of OP, dexamethasone (DEX), and 17 beta-estradiol on rat splenocytes were compared. Dexamethasone was more toxic than OP after 24 hr of culture; 17 beta-estradiol was not toxic. Dexamethasone and OP, but not 17 beta-estradiol, caused significant nuclear condensation after 3 hr of culture (acridine orange staining) or 4 hr of culture (propidium iodide staining). The toxicity of 10(-6) M OP, but not that of 10(-6) M DEX, was eliminated when mouse splenocytes were cultured in Ca2+ -free medium. Significantly more mouse splenocytes containing free 3'-OH DNA ends were detected by activated cell sorter analyses when the cells had been incubated for 4 hr with 10(-4) or 10(-6) M OP or 10(-6) M DEX. The results of these studies demonstrate that OP is toxic to cultured rat and mouse splenocytes and suggest that this toxic effect is exerted, at least partially, through Ca2+-dependent apoptosis.