Inhibition of neutrophil chemotaxis by pig seminal plasma in vitro: a potential method for modulating post-breeding inflammation in sows

The aim of this study was to determine the regulatory role of pig seminal plasma in post-breeding uterine inflammation. Polymorphonuclear neutrophil (PMN) chemotaxis of lipopolysaccharide (LPS)-activated blood plasma or heat-inactivated blood plasma plus LPS containing increasing concentrations of seminal plasma was assessed in chemotactic chambers. Seminal plasma was diluted serially with McCoy's medium to concentrations of 50.0, 25.0, 12.5, 6.2 or 3.1% (v/v) and added to normal or heat-inactivated pig blood plasma that was activated with LPS before or after incubation in a 37 degrees C waterbath for 30 min. Chemotaxis was determined using blood-derived PMNs and was expressed as a percentage of the positive control of LPS-activated blood plasma. A linear dose-dependent suppression of chemotaxis by seminal plasma was observed for blood plasma activated before or after addition of seminal plasma. Compared with the positive control, concentrations of seminal plasma < 6.2% failed to suppress PMN chemotaxis (P < 0.05). A dose-dependent suppressive effect of seminal plasma on heat stable chemotactic components of pig blood plasma was also observed (P < 0.05). A marked suppression was observed at concentrations of seminal plasma > 12.5% of the sample volume (P < 0.05). These results indicate that seminal plasma suppresses chemotactic blood plasma components regardless of formation sequence (pre- or post-activation) or source (normal or heat-inactivated blood plasma). These results indicate that seminal plasma may be necessary in diluted boar semen used for artificial insemination to regulate post-breeding inflammation in sows.

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