A ram epididymal secretory protein shares common antigenic determinants with rat epididymal proteins and human seminal plasma proteins.

Mammalian spermatozoa leave the testis as immature cells unable to fertilize until they have traversed the epididymis. Sperm maturation is an orchestrated series of sequential events occurring at different levels of the epididymis : sperm-zona pellucida binding ability in the proximal epididymis, progressive motility and the ability to penetrate and fertilize the oocyte in the middle epididymis and the ability to initiate normal embryonic development in the distal epididymis (see reviews by Orgebin-Crist, 1986 ; Amann, 1987 ; FournierDelpech and Courot, 1987). In parallel, spermatozoa undergo a variety of surface changes (Hammerstedt and Parks, 1987). Although the functional significance of these changes has not been elucidated, it is believed that some could be related to the processes of sperm maturation. Sperm maturation itself is dependent upon androgen-controlled secretory products of the epididymal epithelium (see review by Orgebin-Crist, 1986). Since inhibitors of protein synthesis block the acquisition of fertilizing ability within the epididymis, particular attention has been focused on epididymal proteins which are secreted upon androgen stimulation and which intereact with the maturing spermatozoa. Such proteins could mediate the androgenic regulation of fertilizing ability of the spermatozoa.