Toxicity of environmental contaminants to fish spermatozoa function in vitro--a review

In vitro techniques for investigating the toxic effects of environmental contaminants (EC) on fish spermatozoa motility kinetics and fertilizing ability are valuable tools to understand toxicity mechanisms and sites of action. In vitro techniques may also be well-suited to studies of endocrine disruption in male fertility in vivo. This review shows ECs to decrease or suppress spermatozoa motility kinetics and fertilizing ability in a dose-dependent manner, with toxic concentrations being much higher than those reported in the aquatic environment. Sites of action depend on EC concentration and duration of exposure. Both instant (immediate) and incubated exposure of spermatozoa to ECs results in damage to the plasma membrane and the axoneme, while disruption of energy metabolism appears only during incubated exposure. Spermatozoa lose fertilizing ability following exposure to ECs in vitro, not only due to inhibition or suppression of the initiation of motility, but also through damage to DNA. This review highlights the significant lack of information about disruption of spermatozoa function associated with exposure to water from polluted areas as well as combined effects of ECs. Specifics of alterations in intracellular signaling cascades involved in the initiation of spermatozoa motility following exposure to sublethal concentrations of ECs remain unknown. Further studies are also needed to elucidate in vitro EC effects during spermatozoa maturation, when spermatozoa acquire the potential for motility.