The effects of the proliferation of the radial arteries of the placenta on oxygen transport to the fetal guinea pig.

The adjustment of placental blood flow during pregnancy is related to progressive structual changes in the placental arteries. In guinea pig, massive growth has also been shown to be associated with widening of the uterine radial arteries. The rate of 3H-thymidine incorporation into uterine radial arteries during pregnancy was studied in guinea pig as a measure of local DNA synthesis. And the oxygen partial pressure was used to investigate how the oxygen transport is done between mother to fetus. During the first half of pregnancy, 3H-thymidine was incorporated at the rate of about 1,000 Bq/mg.h. The initial rate during pregnancy is similar to the rate observed during estrus. This observation suggest that the same factors stimulate DNA synthesis during gestation and estrus. The rate of 3H-thymidine incorporation per vessel length increased with the injected dose of estradiol benzoate. We suppose that estradiol is one of the control factors in DNA synthesis in uterine radial artery. The oxygen partial pressure in amniotic fluid was about 110 mmHg on various days of gestation and no significant changes were observed with time. For these reasons, estrogen is supposed to be one of the control factors in oxygen transport to fetus.