The fate of isotope-labelled uterine spermatozoa in the mouse post coitum

Abstract

Isotopically labelled sperm was used to investigate the fate of the uterine sperm residue not used in the process of fertilization of the mouse. Portion of the sperm present in the uterus exhibiting a copulation plug was removed and replaced by intrauterine injection of sperm labelled either specifically by tritiated thymidine or non-specifically by exposure to a tritium source. The latter label was found more suitable for tracer use although the results with both methods were qualitatively similar. Seventeen hours after injection label was present in sperm in the lumen, in debris associated with polymorphonuclear granulocytes and monocytes in the lumen, in the epithelial and subepithelial coats of the mucosa and in phagocytic cells of the lower abdominal lymph nodes and spleen. The density of labelling was greatest in the sperm itself then fell away sharply and uniformly in the other sites. Label was present at this time in sperm spilled into the peritoneal cavity via the needle track. Associated with this spillage, label was seen in peritoneal polymorpho- nuclear granulocytes and macrophages, in macrophages of the uterine wall, and in phagocytic cells of the lymph nodes and spleen. The density of labelling was greatest in the sperm itself but the density decline in these other sites was less than in these same sites resulting from sperm retained wholly in the uterine lumen. Labelled sperm was present in all experiments in the vaginal lumen. The relation between the density of labelling and the degree of degradation of the sperm products is discussed and it is reasoned that the female cells are exposed to less degraded sperm products as a result of entry via the peritoneal cavity than entry via the uterine mucosa. This route may be thereby more effective as an antigenic stimulant.