Production of glycosaminoglycans by the porcine oviduct in relation to sperm storage

Follicular and oviductal fluids have shown modulatory effects on sperm capa citation of boar spermatozoa in vitro, implicating glycosaminoglycans (GAGs ) in the process. Capacitation in pigs is believed to occur in vivo during storage in the sperm reservoir, where spermatozoa maintain viability and me mbrane stability awaiting ovulation. Exposure to the nonsulphated GAG hyalu ronan induces capacitation in vitro (chlortetracycline-monitored) without e liciting acrosome exocytosis, indicating that it exerts a protective role o n sperm viability. Oviductal fluids (isthmus and ampulla) of cycling sows w ere collected in vivo to disclose temporal changes in concentrations of bot h sulphated and nonsulphated GAGs between late prooestrus and meta-oestrus. Further, heparan-sulphate and hyaluronan were immunohistochemically locali zed in the oviductal tissues of uninseminated and inseminated sows, around the period of ovulation. Concentrations of sulphated GAGs were two-fold hig her than hyaluronan. All tubal GAGs increased significantly from late pro-o estrus and were highest during the pre-ovulatory period before beginning to decrease postovulation, the exception being the ampullar hyaluronan, whose levels remained high towards meta-oestrus. Heparan sulphate (syndecans) an d hyaluronan were both immunohistochemically detected in the endosalpinx. S yndecan-immunolabelling was present in the epithelium and stroma along the tube, whereas hyaluronan was always localized in the lamina propria and mos t of the lining epithelium was negative, during the stages studied. The onl y exception was the sperm reservoir (deep crypts and furrows of the Utero-t ubal Junction (UTJ)/isthmus) where sperm clusters were seen close to the ep ithelial HA-immunolabelling in the inseminated sows, but only pre-ovulatory . The presence of GAGs in the tubal fluid and the conspicuous location of h yaluronan suggest they play a role in the formation and function of the spe rm reservoir.