255 SEMINAL PLASMA PROTEINS: FUNCTIONAL ATTRIBUTES AND POTENTIAL MARKERS OF FERTILITY

Abstract

Mammalian seminal plasma is a complex milieu containing, mostly, secretions of the epididymides and accessory sex glands. After ejaculation, proteins of the seminal fluid interact with sperm and participate in several events, including sperm motility, protection against immune reactions, oxidative processes and microorganisms, interaction with the oviduct epithelium, capacitation, acrosome reaction, and fertilization. Given these aspects, the present talk is focused on seminal plasma proteins and cross-species comparisons of their functional attributes. Experiments that will be presented used gel-based and shotgun proteomics. Binder of sperm proteins are major components of ruminant seminal plasma, while spermadhesins are predominant in the boar and deer (Mazama gouazoubira; Mazama nemorivag) seminal fluid. Annexins (rabbits), clusterin (peccaries: Pecari tajacu), and arginine esterase (coatis: Nasua nasua; dogs) are the most abundant proteins in seminal fluid of other species. Such diversity may reflect differences in how paternal factors modulate fertility. Studies have also reported empirical associations between seminal proteins, sperm freezability, and fertility indexes in ruminants and other domestic species. As evidenced by experiments using IVF, mainly in the bovine, specific seminal proteins influence the fertilizing capacity of both epididymal and ejaculated sperm, as well as early embryo development. In summary, fundamental knowledge gathered by studies of seminal plasma proteome can be used to identify molecular markers of fertility. Availability of such markers will potentially improve the outcome of artificial reproductive technologies. Diversity of seminal plasma composition, however, represents challenges for discovery of fertility markers in unique species. Seminal plasma proteins may also be related to new phenotypes, such as bull differences in sperm survival after sexation.

This research was funded in part by the Brazilian Research Councils (CAPES and CNPq) and Ceara State Foundation for Scientific and Technological Development (FUNCAP).