In vitro phagocytosis of boar spermatozoa by neutrophils from peripheral blood of sows

A considerable number of spermatozoa are used in each sow in routine artifi cial insemination. However, within a few hours after insemination, many spe rmatozoa are phagocytosed by polymorphonuclear leucocytes. Some aspects of sperm transport in the female genital tract in the sow have been thoroughly investigated, whereas little is known about the mechanisms involved in the phagocytosis of spermatozoa, or about which spermatozoa (fresh, capacitate d or dead) are the most susceptible to ingestion by polymorphonuclear leuco cytes. In this study, phagocytosis was investigated by use of an in vitro p hagocytosis assay Polymorphonuclear leucocytes were challenged with either untreated, cold-shocked or frozen-thawed spermatozoa, or with spermatozoa t hat had been treated to induce capacitation in vitro. The influence of seru m on phagocytosis was also investigated. Treatment of the semen to induce c apacitation in vitro considerably reduced the phagocytosis of spermatozoa, whereas crude treatments like cold-shock or freezing and thawing reduced ph agocytosis only in the first 15-30 min of incubation with polymorphonuclear leucocytes. Viable spermatozoa were phagocytosed mainly through a pathway that was independent of complement or other serum components (for example, antibodies). Complement had Little effect on phagocytosis of spermatozoa, b ut did cause acrosomal exocytosis and cell death.