Fate of Nonfertilizing Spermatozoa and Interaction of Spermatozoa with Somatic Cells

Abstract

Of the millions of mammalian sperm inseminated into the female genital tract, only a very few ever reach the site of fertilization. The major mechanism by which excess spermatozoa are eliminated is by leukocytes that invade the uterus (Austin, 1960; Yanagimachi and Chang, 1963b; Bedford, 1965; Mahajan and Menge, 1966; Moyer et al., 1967) and uterine cervix (Moyer et al., 1970) after copulation. Phagocytosis of spermatozoa by epithelial cells of the endometrium (Moyer et al., 1967) and oviducal mucosa (Austin, 1960; Zamboni, 1971a) has also been reported. Nonfertilizing sperm persisting in the female tract may also occasionally be phagocytized by embryos at the two-cell (Thompson and Zamboni, 1974) and blastocyst (Tachi and Kraicer, 1967; McReynolds and Hadek, 1971) stages. In rodents and lagomorphs clearance is rapid, occurring within 24–36 hr after copulation (Howe, 1967; Bishop, 1969). However, little is known concerning the clearance from the female tract of spermatozoa in species such as the dog, horse, and ferret in which sperm survive much longer, a property possibly correlated with the longer estrus period in these mammals.