Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and persistent environmental contaminants. Some PAHs are carcinogens and may affect the male reproductive system. Therefore, we exposed cultured rat Sertoli cells to a variety of PAHs to determine possible direct toxic effects on the cells of the seminiferous epithelium. Sertoli cells were chosen because they support germ cell development and maintain spermatogenesis. Sertoli cells were isolated from 19-21-day-old male rats and cultured in medium containing 0.08% dimethylsulfoxide as vehicle or in the presence of a variety of PAHs. In the first set of experiments, cultured Sertoli cells were incubated in the presence of 10(-4) M, 10(-6 )M, 10(-8) M, 10(-12) M, and 10(-16) M fluoranthene (FL) for 24 hr. After 24 hr, FL at 10(4), 10(-6), and 10(-8) M killed significant numbers of Sertoli cells as revealed by cell viability determinations. Sertoli cells cultured in the presence of 10(-6) M and 10(-8) M FL showed morphologic changes. Cell protein levels were decreased and lactate production in the medium increased in a concentration-dependent manner. In addition, Sertoli cells exposed to 10(6) M and 10(-8) M FL exhibited altered F-actin and alpha-tubulin distributions compared with untreated controls. Because FL killed about 62% of cells at 10(-4) M (100 micro g/mL) and 48% of cells at 10(-6) M (1 micro g/mL), increased lactate production about 3-fold at both concentrations, and decreased cell protein by half at 10(-4) M (100 micro g/mL), we decided to use a range of concentrations between 10 and 100 micro g/mL for the second set of experiments using benz[a]anthracene (BaA), benzo[a]pyrene (BaP), or benzo[b]fluoranthene (BbF). After 24 hr, BaA (100 micro g/mL), BaP (50 and 100 micro g/mL), and BbF (100 micro g/mL) significantly increased lactate level in the medium in a concentration-dependent manner. In a third set of experiments, cells were treated in culture uniformly with only 10 micro g/mL FL, BaA, BaP, or BbF for 24 hr. The cytotoxic effects exerted by these PAHs tested resulted in different apoptotic responses as characterized by in situ fluorescence staining. Microscopic analysis of apoptotic cells demonstrated nuclei of reduced size and labeled 3 -OH DNA ends when Sertoli cells had been incubated for 24 hr with 10 micro g BaP or BbF, but not with vehicle, media, FL, or BaA. Thus, our results demonstrate that the toxic effects of BaA and BbF on Sertoli cells are exerted through apoptosis, whereas FL and BaA do not elicit the apoptotic response.