Induction of uterine prostaglandin H synthase 2 by estradiol following fetal adrenalectomy.

Journal Article

In sheep, fetal cortisol stimulates the conversion of progesterone to estradiol in late gestation initiating labor. It is unclear whether an intact fetal hypothalamic-pituitary-adrenal (HPA) axis is required to induce the estradiol-triggered subsequent endocrine changes including enhanced intrauterine prostaglandin (PG) synthesis associated with the onset of labor. We have shown that maternal estradiol administration stimulates PG H synthase (PGHS)-2 expressions in pregnant ovine intra-uterine tissues. The current study was undertaken to determine whether the fetal adrenal mediates estradiol's stimulation of the intrauterine PGHS-2 in pregnant sheep. Placenta, myometrium, and endometrium were collected from two groups of ewes at 123-127 d of gestational age (dGA) after fetal adrenalectomy and vehicle treatment (ADX; n = 5); or fetal ADX and maternal estradiol administration (5 mg twice a day for 2 d, ADX+E2, n = 5). PGHS-2 mRNA and protein were analyzed by Northern and Western Blot analyses in both groups and presented as the ratios to beta actin mRNA for Northern and G protein beta subunit for Western blot analysis. Fetal plasma cortisol was measured by radioimmunoassay. Data were analyzed by Student's t test. Fetal plasma cortisol levels were low in ADX and ADX+ E2 groups (<6 ng/mL). The cervix of all ADX+E2 treated ewes was dilated at necropsy. Three out of five ADX+ E2-treated ewes delivered within 48 h. The cervix was closed in all fetal ADX ewes at necropsy. PGHS-2 mRNA and protein increased (p < 0.05) in myometrium and endometrium, but not placenta in ADX+E2-treated ewes compared with ADX group. These data provide the first in vivo evidence for estradiol upregulation of intrauterine PGHS-2 in late gestation in the absence of an intact fetal HPA axis. Thus, the fetal adrenal is not required to mediate estradiol's stimulation of uterine PGHS-2 expression associated with the onset of labor.

Full Text

Duke Authors

Cited Authors

  • Wu, WX; Wolf, R; Chakrabarty, K; Collins, V; Unno, N; Nathanielsz, PW; Rose, JC

Published Date

  • March 2005

Published In

Volume / Issue

  • 26 / 2

Start / End Page

  • 153 - 159

PubMed ID

  • 15888927

Pubmed Central ID

  • 15888927

Electronic International Standard Serial Number (EISSN)

  • 1559-0100

International Standard Serial Number (ISSN)

  • 1355-008X

Digital Object Identifier (DOI)

  • 10.1385/endo:26:2:153

Language

  • eng