Role of a Uterine Endopeptidase in the Implantation Process of the Rat

Abstract

The genital tract fluids of mammalian species provide the milieu in which oocyte maturation, fertilization, early development of cleaving embryos, and blastocyst implantation take place. Proteins secreted into the lumen of the female genital tract, especially those regulated by reproductive hormones, may participate crucially in these reproductive events. Studies on the uterine lumenal proteins of mice (Gore-Langton and Surani, 1976) and rats (Surani, 1975, 1976) suggested a hormone-controlled sequence of protein changes that coincide with the time of implantation. Joshi et al. (1970) have isolated and characterized an endopeptidase from estrous fluid obtained from proestrous rats and from immature or overiectomized rats treated with estradiol. The uterine peptidase demonstrated strong affinity to sperm membrane and zona pellucida. Immunological studies (Joshi and Murray, 1976) showed that the enzyme was unique to uterus and oviduct and was not detected in serum. Appearance of the enzyme on Day 5 of pregnancy (Joshi and Murray, 1976) suggested a role for this protein in the implantation process (Rosenfeld and Joshi, 1977).