Role of epididymal secretory proteins in sperm maturation with particular reference to the boar

This review considers the role of proteins secreted by the epididymis on post-testicular sperm maturation and storage. Two-dimensional gels show that 150 to 200 proteins are secreted into the epididymal lumen. Most are secreted in relatively small amounts; in rams, for example, fewer than ten contribute 90% of the total secretion and only two contribute 52% of the total protein secreted. Most of the proteins are confined to specific regions of the epididymis. The changing pattern of protein secretion along the epididymis corresponds to change in surface protein on spermatozoa, but no epididymal proteins have been identified that appear to be directly involved in modifying the sperm membrane. Most of the major proteins that have been identified seem to be playing a homeostatic role in maintaining the epididymal milieu for spermatozoa.