Fate and distribution of seminal plasma proteins in the genital tract of the female rat after natural mating.

This paper describes the distribution and fate of seminal plasma proteins in the rat female genital tract after insemination, using immunological detection in tissue sections and in fluids collected from different regions. The localization of seminal plasma proteins in the uterus and the vagina correlated with that of spermatozoa, suggesting that passive transport mechanisms operate in these regions. No seminal plasma proteins were detected in the oviduct, indicating that their presence is probably restricted to the uterine environment. Possible mechanisms for eliminating seminal plasma molecules after copulation include leakage from the uterus after relaxation of the cervical muscles and endocytosis by the endometrial cells. Large amounts of both vesicular and coagulating gland proteins were detected in the vagina of females at the time of cervical relaxation, indicating that the first mechanism of leakage from the uterus after cervical relaxation operates. Immunocytochemical procedures were used and seminal vesicle antigens were detected inside uterine epithelial cells, which indicates that endocytosis is also a mechanism for elimination of these molecules after copulation. Western blot results suggest proteolytic cleavage as a third mechanism. However, coagulating gland antigens are neither endocytosed nor cleaved, and their elimination takes place only by backflow to the vagina. The seminal plasma distribution in experimental situations in which sperm transport is altered was also studied. The implications of our findings for mechanisms of sperm transport in the female are discussed.