The synthesis and accumulation of polyamines in reproductive organs of the rat during pregnancy

Abstract

The pregnancy of the rat brings about profound changes of the accumulation, biosynthesis and biodegradation of the polyamines putrescine, spermidine and spermine in the reproductive tissues. 1. 1. In the ovary, the concentration of all polyamines increased markedly around the 12th day of pregnancy. In the uterus, only the concentration of spermine rose at that time. The concentration of putrescine more than doubled in the fetal part of the placenta around the 15th day of pregnancy, while the low content of putrescine in the maternal placenta did not appreciably change during the progress of pregnancy. Both parts of rat placenta contained relatively high initial concentrations of spermine, which however, rapidly decreased until the term. 2. 2. The activity of ornithine decarboxylase (EC 4.1.1.17) was remarkably high in the placental tissue. The fetal part of the placenta exhibited higher ornithine decarboxylase activity from the very beginning and the enzyme activity also remained at high levels throughout the pregnancy. The initially high ornithine decarboxylase activity in the maternal part of the placenta rapidly declined during pregnancy, almost totally disappearing just before the term. Ornithine decarboxylase activity was very low in the uterus during the early days of pregnancy, however, rapidly increased a few days after the implantation. Uterine ornithine decarboxylase activity reached a maximum on day 12 to 14 of pregnancy and then swiftly decreased. 3. 3. Both parts of the placenta contained high diamine oxidase (EC 1.4.3.6) activity, which, however, rapidly disappeared in the fetal part of the placenta. Although considerably decreasing, the activity of diamine oxidase still was remarkably high in the maternal placenta until the term. No diamine oxidase activity was found in the uterus of normally cycling rats. The enzyme activity was also undetectable in the uterus during the early pregnancy, but abruptly appeared on day 10 of pregnancy, reached a maximum around the 15th day of pregnancy, and thereafter gradually decreased until the term. 4. 4. The changes of the activity of adenosylomethionine decarboxylase (EC 4.1.1.50) in the uterus and placental tissues resembled those changes found in ornithine decarboxylase activity. The activity of adenosylmethionine decarboxylase also rapidly decreased after day 12 of pregnancy. 5. 5. Uterine diamine oxidase was partially purified (about 30-fold) and its substrate specificity was determined. Diamines putrescine, cadaverine and 1,3-diaminopropane serve as most efficient substrates for the enzyme. Some evidence is presented as to indicate that also spermidine and spermine were oxidized by the enzyme, although at much slower rate than the diamines. While the role of diamine oxidase acitivity in determining the tissue concentration of putrescine remains to be established, it appeared than in tissues devoid of diamine oxidase activity (ovary) and tissues exhibiting only low diamine oxidase activity (fetal placenta after day 13) the concentration of putrescine closely followed the activity of ornithine decarboxylase, whereas in tissues containing high diamine oxidase activity (uterus and maternal placenta) this kind of correlation was totally lacking. 6. 6. It is possible that the secretion of placental luteotrophin, which resembles growth hormone in its structure and biologic action, regulates the accumulation and biosynthesis of polyamines at least in some of the reproductive tissues of pregnant rat.