Effects of single polychlorinated biphenyls on the morphology of cultured rat tubuli seminiferi

The effects of single polychlorinated biphenyls (PCB) on isolated tubuli se miniferi of the rat were studied. Freshly isolated rat tubuli seminiferi we re prepared according to their transillumination pattern, i.e. dark or pale . Tubuli seminiferi with the dark pattern included stages II to VIII and tu buli with the pale pattern represented stages IX to XIV and stage I of the seminiferous cycle. Afterwards, tubuli seminiferi were exposed to single po lychlorinated biphenyls for 5 or 24 h in vitro. PCB 126, PCB 77, and PCB 11 8 were used in final parts per billion (p.p.b.) concentrations as determine d by quantitative PCB analysis. Eventually, the specimens were plastic embe dded, cut into semithin sections, stained, and morphology was evaluated by light microscopy. Single PCB congeners induced morphological alterations in cultivated rat tubuli seminiferi in a time- and stage-dependent manner. Ef fects comprised loosened intercellular contacts between germ cells and Sert oli cells as well as cellular fragmentation in the layer of round spermatid s. Early spermiogenesis seems particularly susceptible to single PCB congen ers in concentration of background magnitude. The target cell has still to be discovered.