Histochemical studies on the peroxidase localization in the rat ovary and uterus during various reproductive stages

Studies on peroxidase-catalyzed formation of progesterone

Subcellular fractions of pregnant rabbit ovary at day six of gestation catalysed the formation of progesterone from pregnenolone (3 beta-hydroxy-5-pregnen-20-one). The microsomal fraction was found to have maximum activity. The enzyme needed hydrogen peroxide for its activity. In vitro studies using horseradish peroxidase also showed similar conversion and this was stimulated 200% in the presence of ascorbic acid. Ascorbate thus appears to perform a catalytic role in this conversion. The importance of peroxidase in luteal steroidogenesis is indicated.

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.