Components in seminal plasma regulating sperm transport and elimination

Abstract Seminal plasma has been suggested to be involved in sperm transport, and as a modulator of sperm-induced inflammation, which is thought to be an important part of sperm elimination from the female reproductive tract. This article reports on recent experiments on the importance of seminal plasma components in sperm transport and elimination. In Experiment 1, hysteroscopic insemination in the presence ( n  = 3) or absence ( n  = 3) of 2 ng/mL PGE showed an increased portion of spermatozoa crossing the utero-tubal junction in the presence of PGE in two mares, while no difference was observed between treatments in a third mare. In Experiment 2, whole seminal plasma, heat-treated seminal plasma (90 °C for 45 min), and charcoal-treated seminal plasma were added to: (1) sperm samples during opsonization prior to polymorphonuclear neutrophil(s) (PMN)-phagocytosis assays ( n  = 5); or to (2) phagocytosis assays ( n  = 5). Opsonization of spermatozoa was suppressed in the presence of whole seminal plasma, compared with samples without seminal plasma ( p p p p n  = 3): (1) seminal plasma (SP), (2) extender; (3) ammonium sulfate precipitated seminal plasma proteins with protease inhibitor (SPP + ); or (4) ammonium sulfate precipitated seminal plasma proteins without protease inhibitor (SPP − ). Treatment was observed to impact binding and phagocytosis of viable and non-viable spermatozoa ( p + suppressed PMN-binding and phagocytosis of viable sperm. This effect was also seen, but to a lesser degree, in SPP − treated samples. Non-viable spermatozoa showed less PMN-binding and phagocytosis than live sperm in the absence of SP. The addition of SP promoted PMN-binding and phagocytosis of non-viable spermatozoa. SPP − treated samples also restored PMN-binding of non-viable spermatozoa. The addition of protease inhibitors removed this effect. In Experiment 4, seminal plasma proteins were fractionated based on MW by Sephacryl S200 HR columns (range 5000–250,000 kDa). Fractionated proteins were submitted to sperm-PMN binding assays. A protein fraction