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Progesterone Synthesis by Ovine Fetal Cotyledons In Vitro^{1, 2,}

Oregon State University³, Corvallis 97331

Abstract

Ten mature ewes exhibiting normal estrous cycles were bred to fertile rams and assigned randomly in equal numbers to two groups. Animals were sacrificed on days 45 and 55 of pregnancy. Samples of minced fetal cotyledons from placentae of ewes in each group were treated in vitro with 50 µg luteinizing hormone (LH), 50 µg pregnenolone or 50 µg pregnenolone and 50 µg LH. Following incubation extracts of the tissue samples were analyzed for progesterone by use of radioimmunoassay. Progesterone concentrations of fetal cotyledons were not different between days 45 and 55 of pregnancy. Tissues incubated with pregnenolone had significantly higher (P<.01) concentrations of progesterone than those incubated without pregnenolone. Addition of LH stimulated a further increase in the in vitro conversion of pregnenolone to progesterone by fetal cotyledons (P<.05).

These data suggest that ovine fetal cotyledons possess the capacity to synthesize progesterone prior to day 50 of gestation at which time the placenta begins producing progesterone in concentrations sufficient to maintain pregnancy. Luteinizing hormone may also serve some regulatory function in placental steroido-genesis.

¹ Technical Paper No. 3947, Agricultural Experiment Station, Oregon.

² Appreciation is expressed to Dr. John À. Resko and Mr. Henry Stadelman, Oregon Regional Primate Center, for assistance in adapting progesterone radioimmunoassay techniques to our laboratory and to the Endocrine Study Section, National Institutes of Health, for the gift of NIH-LH-S-9.

³ Department of Animal Science.

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