Ascorbate and peroxidase changes during pregnancy in albino rat and Swiss mouse

From the 1st to 6th days of pregnancy in the rat, while the blastocyst is still in the fallopian tube, there is high peroxidase activity in the corpus luteum, the blastocyst, and there is high peroxidase activity in the endometrium. On day 8 of pregnancy, peroxidase activity in the corpus luteum begins to fall rapidly, and there is a sharp rise in the peroxidase activity of the uterine endometrium. In all these tissues an inverse relationship exists between peroxidase and ascorbate content. We suggest the involvement of the peroxidase-ascorbate system in the mechanism of the extended function of the corpus luteum during pregnancy and a role for free radicals in the process of implantation of the blastocyst in the uterus.