Secretory proteins from the epididymis and their clinical relevance

The literature pertaining to epididymal proteins and their functions in fertilization is reviewed. Animal studies have indicated that specific epididymal proteins may be involved in aspects of sperm motility, sperm-zona binding and the acrosome reaction. If analogous proteins in the human exist, use could be made of them in the andrology clinic. Currently, only one specific epididymal protein (alpha-glucosidase) is routinely measured for semen analysis. Glucosidase secretion, in addition to reflecting inflammation of the organ, is used in conjunction with other markers of human fertility to identify patients with ductal occlusion for whom bypass operations may be useful therapy. Glucosidase inhibitors have been used to improve the assay, by establishing true semen blank values, and to quantify histochemical activity in frozen tissue sections. From its localization in the human corpus and cauda epididymidis, neutral glucosidase can not be used to identify occlusion in the proximal regions of the duct. Other proteins may be valuable markers of these regions. In the future, other specific proteins of epididymal origin found in seminal fluid could well illuminate dysfunction of the organ in cases of infertility or be end-points of the disruptive action of drugs aimed at the epididymis.