Corticotropin-Releasing Hormone Directly and Preferentially Stimulates Dehydroepiandrosterone Sulfate Secretion by Human Fetal Adrenal Cortical Cells*

Abstract

Estrogens produced by the placenta play a pivotal role in the endocrine control of pregnancy and induce many of the key changes involved in parturition. The placentae of humans and higher primates use the C19 androgen dehydroepiandrosterone sulfate (DHEA-S) supplied by the fetal adrenals as the principal substrate for estrogen synthesis. Thus, secretion of androgens by the fetal adrenals may be central to the process of primate parturition. The timing of human parturition also is correlated with placental CRH concentrations in the maternal circulation. Because the mechanisms that regulate DHEA-S production by the fetal adrenals are incompletely understood, we examined whether there is a functional relationship between CRH and steroid production by human fetal adrenal cortical cells. Using Northern blot analysis, we detected messenger RNA transcripts (2.7 kb) encoding the type-1 CRH receptor in total RNA extracted from midgestation human fetal adrenals, suggesting that the fetal adrenal cortex may be directly responsive to CRH. To test this, primary cultures of human fetal adrenal cortical cells were exposed to human CRH. Human CRH increased DHEA-S production by cultured human fetal adrenal cortical cells in a dose-dependent fashion, with an ED50 of 10-100 pmol/L. Human CRH was as effective as ACTH at stimulating DHEA-S production; however, it was 70% less potent than ACTH at stimulating cortisol production, indicating that its actions were preferentially directed toward increasing DHEA-S synthesis. Consistent with this thesis, we found that CRH increased abundance of messenger RNA encoding cytochrome P450 cholesterol side-chain cleavage and 17alpha-hydroxylase/17,20 lyase but not 3beta-hydroxysteroid dehydrogenase in adrenal cells. CRH did not alter cell number, indicating that it is not mitogenic for fetal adrenal cortical cells. These data demonstrate a direct functional interaction between CRH and the fetal adrenal. Therefore, placental CRH production, which rises exponentially during human pregnancy, may play a key role in promoting DHEA-S production by the fetal adrenals, which could lead to increasing placental estrogen synthesis and contribute to the process of parturition in humans.