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

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Abstract
Progesterone and [DELTA] 4-pregnene-20[beta]-ol-3-one (20[beta]-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. Progesterone and 20[beta]-ol in corpora lutea increased from non-detectable levels on Day 2 to mean levels of 73.2 and 7.0 [mu]g/g, respectively, on Day 14 of the estrous cycle and thereafter showed a precipitous decline to the next estrus. 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 [mu]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[beta]-ol found in jugular vein plasma.