Toxic effects of octylphenol on cultured rat spermatogenic cells and Sertoli cells

Alkylphenols, including the estrogenic 4-tert-octylphenol (OP), are environmental pollutants. Because administration of OP to adult male rats impairs spermatogenesis and OP has been shown to be toxic to aquatic animals and to mammalian splenocytes in vitro, we studied whether OP exerts direct toxic effects on cultured spermatogenic cells and Sertoli cells isolated from male rats. Cell viability was assessed with a Live/Dead Eukolight viability/cytotoxicity kit. Culture of mixed spermatogenic cells from adult rats with 10(-8) M OP or Sertoli cells from 19- to 21-day-old rats with 10(-12) M OP, but not with 0.08% EtOH (vehicle) or 10(-6) M 17beta-estradiol (E2) or dexamethasone (DEX), significantly decreased the percentage of viable cells after 24 h of treatment. None of the treatments significantly altered total cell number. Flow cytometric analyses of spermatogenic cells revealed that exposure to 10(-4) or 10(-6) M OP yielded abnormal relative ploidy classes. Four hours of treatment with 10(-6) M OP, but not with 10(-6) M E2 or DEX, caused significant chromatin condensation in Sertoli cells as observed with acridine orange staining. The decreased percentage of viable cells after 24 h of exposure to 10(-6) M OP remained when Sertoli cells were cultured in Ca2+-free medium. Sertoli cells contained nuclei of reduced size and labeled 3'-OH DNA ends as detected by microscopic analyses when the cells had been incubated for 24 h with 10(-6) M OP but not with vehicle or 10(-6) M E2 or DEX. The results demonstrate that OP, but not E2 or DEX, is directly toxic to cultured rat spermatogenic cells and Sertoli cells and suggest that this toxic effect in Sertoli cells is exerted through Ca2+-independent apoptosis.