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1 Respiratory Medicine, The Hospital for Sick Children, Toronto, Ontario M5G 1X8; and 2 Department of Pathology, Meakins-Christie Laboratories, McGill University, Montreal, Quebec, Canada H2X 2P2
Pulmonary glucocorticoid receptor (GR) is
essential to timely preparation for the onset of breathing air at
birth. We have previously used primary culture of late-gestation fetal
rat lung cells to demonstrate differential regulation of GR by
glucocorticoid depending on cell type. In this study, we hypothesized
that the action of glucocorticoid on GR mRNA expression and protein
elaboration in lung cells might be modulated by interactions present in
vivo but not in primary culture. Given that male sex hormone (androgen) has an inhibitory effect on antenatal lung development, we also postulated that androgen would decrease antenatal lung GR. We report
that antenatal maternal injection of the glucocorticoid dexamethasone
(1 mg/kg) enhanced fetal lung cellular levels of GR mRNA and protein as
assessed by in situ hybridization and immunocytochemistry (ICC),
respectively. ICC was performed using polyclonal rabbit anti-human
antibody that reacts with rat GR whether bound to ligand or not and
does not interfere with GR binding to DNA. Levels of GR mRNA and
protein were enhanced in cells throughout all areas of the lung tissue,
suggesting that interactions occurring in intact tissue may override
the previously reported direct inhibition by glucocorticoid of GR
protein elaboration in isolated fetal rat lung epithelial cells.
Furthermore, antenatal administration of the androgen
5
-dihydrotestosterone (0.2 mg/kg) reduced tissue levels of GR mRNA
and protein, consistent with androgenic inhibition of antenatal lung
development by decreasing GR. We conclude that glucocorticoids and
androgens exert opposite effects on fetal lung GR.
dihydrotestosterone; dexamethasone; lung development; in situ hybridization
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