Sources of Progestins in the Pregnant Cow

Progesterone and A~-pregnene-20~-ol-3-one were assayed, usino' paper chromatography and ultraviolet spectra. Neither progestin was detected in the placenta or uterine venous blood of a Jersey heifer pregnant 258 days. The blood, adrenals, and testis of the fetus were negative for progestins. The ovaries contained an estimated 50 ~g. of progesterone (adrenals < 10/~g.) and 5 /xg. of A~-pregnene-20/~-ol-3-one. Six additional assays of cow placentae have been negative for progesterone. Corpora lutea (five assays involving three each) contained approximately 90% of the progesterone and all of the A'-pregnene-20/~-ot-3-one found in the ovaries ~f cows. The remaining progesterone was in the ovaries from which the corpora lutea were' reumved. Progesterone r,~nged from 6.4 to 15.2 tLg/g in luteal tissue. The lowest concentration was from late-pregnant and the highest from nonpregnant cows.