title: Effect of betamethasone on the expression of dopamine D1 receptor mRNA in the developing rabbit adrenal gland.
abstract: BACKGROUND
  Antenatal corticotherapy is widely used to enhance pulmonary fetal maturation in cases in which premature birth is likely. The adrenal gland, which has a key role in controlling fetal and neonatal adaptation, appears to be a target organ of glucocorticoids.
  
  
  OBJECTIVE
  The aim of this study was first to determine the ontogenic profile of dopamine D1 receptor (DA D1-R) messenger RNA (mRNA) in the rabbit. The effects of antenatal exposure to exogenous corticoids on levels of adrenal DA D1-R mRNA expression were examined.
  
  
  METHODS
  Pregnant rabbits free of any treatment or handling before delivery were chosen for the study of DA D1-R mRNA ontogenic profile. For the study of the antenatal exposure to exogenous corticoids, pregnant rabbits were given 2 injections of either betamethasone 0.1 mg/kg or saline 0.1 mL/kg. DA D1-R mRNA expression was determined using northern blot analysis at 4 developmental ages: fetus (at 27 days of gestation), 1 day of age, 25 days of age, and adulthood. Rabbits were allocated to their respective group (treated or untreated) depending on maternal treatment (betamethasone or saline, respectively).
  
  
  RESULTS
  Four pregnant rabbits were used for the ontogenic-profile group, which comprised 11 fetuses, seven 1-day-old rabbits, four 25-day-old rabbits, and 2 adults. Six other pregnant rabbits received betamethasone; 6 saline. The treated group comprised 12 fetuses, twelve 1-day-old rabbits, four 25-day-old rabbits, and 3 adults. The untreated group comprised 12 fetuses, fifteen 1-day-old rabbits, five 25-day-old rabbits, and 3 adults. DA D1-R mRNA was expressed in rabbit adrenal glands from the fetal period to adulthood and this expression was not age dependent. Moreover, antenatal corticotherapy induced a significant increase in respective DA D1-R mRNA levels of 20%, 15%, and 8% in treated fetuses, 1-day-old rabbits, and 25-day-old rabbits compared with the untreated groups (P <0.003, 0.003, and 0.005, respectively). This increase was not observed in adulthood.
  
  
  CONCLUSIONS
  In the rabbits in this study, DA D1-R mRNA expression in the adrenal gland began during gestation. Its expression was not age dependent but was rapidly modified by antenatal exposure to betamethasone. These corticoid-induced changes, observed until late infancy, did not occur in adulthood.
authors.affiliation: JE 2164 Neonatal Adaptation and Development, Henri Poincaré Nancy1 University, Academic Regional Maternity Hospital, Nancy, France, and ; Unit of Research in Perinatology, Academic Hospital, Pavillon Saint François d'Assise, Laval University, Quebec, Canada.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Labaune
authors.affiliation: JE 2164 Neonatal Adaptation and Development, Henri Poincaré Nancy1 University, Academic Regional Maternity Hospital, Nancy, France, and.
authors.forename: Marie-Jeanne
authors.initials: MJ
authors.lastname: Boutroy
authors.affiliation: Unit of Research in Perinatology, Academic Hospital, Pavillon Saint François d'Assise, Laval University, Quebec, Canada.
authors.forename: Aida
authors.initials: A
authors.lastname: Bairam
keywords: adrenal gland; antenatal corticotherapy; development; dopamine D1 receptor