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In Vitro Studies on the Steroid Synthesis by the Placenta of the Cow between Days 200 and 255 of Gestation
Author(s) -
Hoffmann B.,
Eggers C.R.,
Wagner W.C.,
Ellendorff F.
Publication year - 1991
Publication title -
reproduction in domestic animals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.546
H-Index - 66
eISSN - 1439-0531
pISSN - 0936-6768
DOI - 10.1111/j.1439-0531.1991.tb01535.x
Subject(s) - pregnenolone , estrone , endocrinology , medicine , androstenedione , epitestosterone , steroid , in vivo , placenta , chemistry , testosterone (patch) , dexamethasone , trophoblast , estrogen , in vitro , biology , pregnancy , fetus , androgen , biochemistry , hormone , genetics , microbiology and biotechnology
Contents: Placentomes were romoved from 4 to 6 cows before/after treatment with dexamethasone (DXMS) at days 200/205, 220/225, and 250/255 of pregnancy. Preparations of cotyledonary tissue were first perfused with plain HEPES buffered medium 199 (rinsing fraction), followed by the addition of either 3H‐androstenedione and 3H‐pregnenolone or unlabelled cholesterol and pregnenolone as substrates. As indicated by examining the rinsing fractions from untreted animals estrone concentrations. (output) increased from day 200 to day 250 of pregnancy, treatment with DXMS led to a further significant increase on all days examined. Concomitantly with this increase a decrease in pregnenolone and progesterone was observed. Distinct effects of substrate additon were limited to the transformation of 3H‐pregnenolone into 3H‐testosterone/epitestosterone (yield ˜ 8%), furtheron the addition of unlabelled pregnenolone (but not of cholesterol), significantly increased progesterone synthesis as determined by radio immunoassay. Neither these nor other results published till now account for the high estrogen production by the bovine placenta on in vivo conditions. It is concluded that the in vitro systems used so far not or only in part reflect the in vivo conditions necessary to allow complete expression of the steroidogenic capacity of the bovine trophoblast .