Progestin Levels in Jugular and Ovarian Venous Blood, Corpora Lutea, and Ovaries of the Nonpregnant Bovine

Summary Progesterone and Δ 4 -pregnene-20 β -ol-3-one (20 β -ol) were chemically assayed in 42 corpora lutea, ovaries (with corpora lutea removed), ovarian venous blood plasma, and jugular venous blood plasma samples collected from 31 non-pregnant dairy cows and heifers. Corpus luteum weights and progestin (progesterone plus 20 β -ol) content of corpora lutea increased significantly during the first 14 days of the estrous cycle and showed a precipitous decline to the next estrus. Total progestins in the ovary increased significantly to Day 11 postestrus, but levels were generally less than 2.0 μ g/g. No progestin was detected in ovarian venous plasma at estrus or one day following estrus, but progestin concentrations in this plasma increased significantly from Day 2 of the estrous cycle to a peak value of 6.2 μ g/ml on Day 15. Ovarian venous blood plasma progestins were significantly correlated to day of the cycle (r = 0.78) and corpora lutea concentrations of progestin (r = 0.55). Progesterone concentrations in jugular vein plasma did not reflect the stage of the cycle, progestin levels in tissues, or progestin concentrations in ovarian venous plasma. In no case was 20 β -ol found in jugular vein plasma.