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 p lasma 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 s eminal plasma was assessed in chemotactic chambers. Seminal plasma was dilu ted 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 tha t was activated with LPS before or after incubation in a 37 degreesC waterb ath for 30 min. Chemotaxis was determined using blood-derived PMNs and was expressed as a percentage of the positive control of LPS-activated blood pl asma. A linear dose-dependent suppression of chemotaxis by seminal plasma w as observed for blood plasma activated before or after addition of seminal plasma. Compared with the positive control, concentrations of seminal plasm a < 6.2% failed to suppress PMN chemotaxis (P < 0.05). A dose-dependent sup pressive effect of seminal plasma on heat stable chemotactic components of pig blood plasma was also observed (P < 0.05). A marked suppression was obs erved at concentrations of seminal plasma <greater than> 12.5% of the sampl e 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). Th ese results indicate that seminal plasma may be necessary in diluted boar s emen used for artificial insemination to regulate post-breeding inflammatio n in sows.