PROGESTERONE LEVELS IN THE RABBIT OVARIAN VEIN BLOOD THROUGHOUT PREGNANCY12

The importance of progesterone in maintaining pregnancy in the ovariectomized rabbit is well established. A more thorough understanding of the progestational function of the ovary was attempted through the direct measurement of the values of progesterone in the ovarian venous blood at various stages of pregnancy. Blood was extracted by a method similar to that of Butt and Zander. Qualitative identification and quantitation of progesterone was based on chromatography, U.V. absorption, isotope dilution and infra-red analysis. The concentration of progesterone was found to rise gradually to reach a peak of 2.36 μg/ml. at mid-pregnancy; this was followed by a gradual decline in the second half of the pregnancy, with consistent low values of about 0.41 μg/ml, two days prior to parturition. Similar determinations were made on peripheral blood. The curve was similar to that of the ovarian vein in its pattern but with lesser concentration. A ratio of about 1:5 was evident throughout.