Utility of infertile male models for contraception and conservation.

Epididymal defects in infertile domestic species and transgenic mice demonstrate the role of the epididymis in influencing sperm function. Spermatozoa from these males cannot negotiate the female tract as they fail to regulate their volume. The latter is necessary to counter the osmotic stresses encountered in the female tract. Reduced epididymal provision of osmolytes or their premature loss is discussed as probable causes of failed volume regulation. Measuring cell volume regulation for diagnosis of male infertility and blocking it as a means to male contraception are briefly considered. Unchecked human population growth is destroying habitats supporting vulnerable and endangered species. Genome resource banks have been established to preserve spermatozoa of genetically valuable individuals. As cryopreservation stresses spermatozoa osmotically, this process could jeopardise volume regulation with consequences for fertility. Knowledge of sperm volume regulation and the uptake of organic solutes may permit improvement in sperm storage and prevent osmolyte-related cryodamage.