Estrogen is produced in large amounts during pregnancy from both maternal and fetal precursors by placental aromatase. Estrogen's importance in pregnancy and the initiation of labor is apparent from its numerous suggested roles: the control of placental blood flow, increasing in prostaglandin production, increasing myometrial Gap junctions, and increasing myometrial alpha-adrenergic, oxytocin and serotonin receptors. Maternal estrogen (estriol) levels have also been used as a measure of fetal well-being, especially in diabetic pregnancies. Whether placental aromatase is hormonally controlled is controversial. Estrogen levels steadily increase during pregnancy in rough proportion to placental mass suggesting lack of hormonal control. Conversely, many reports have suggested that estrogen is modulated by cAMP-dependent processes. Specifically, LH, hCG, and cAMP analogs increase estrogen production in placental organ culture and placental perfusion experiments. Additionally, cAMP analogs increase estrogen production in placental tumor cell lines. This study will test the hypothesis that cAMP directly effects placental estrogen production by activating cAMP dependent protein kinase with resultant phosphorylation and activation of the estrogen producing enzyme, aromatase, or by increasing aromatase mRNA transcription or translation. We will also examine aromatase regulation by cAMP dependent processes in diabetic pregnancies. Initially we will purify the components of placental aromatase to homogeneity and raise antibodies to these components. Placental explants, trophoblastic cells, and aromatase in a reconstituted membrane system will be exposed to agents which activate the cAMP cascade. Changes in aromatase activity will then be correlated with changes in phosphorylation or concentration of aromatase components by immunoprecipitation of the radiolabelled components, followed by SDS polyacrylamide gel electrophoresis and autoradiography. cAMP induced changes in specific aromatase mRNA production will also be determined by hybridization with a labelled cDNA probe. Many hormones which raise cellular cAMP (catecholamines-BAR, LH, hCG, prostaglandins) are elevated in pregnancy or near delivery. Drugs such as ritodrine, given to inhibit premature labor, may also elevate cAMP levels in placenta. If cAMP modulates placental aromatase, changes in estrogen levels in nearby structures such as the myometrium or fetal membranes could result in major effects upon the pregnancy.
Showing the most recent 10 out of 31 publications
