Effect of dexamethasone on insulin-like growth factor–1 expression in a rabbit model of growth retardation

Background/Purpose: The maternal administration of steroids promotes fetal maturative effects in the gastrointestinal tract. To determine if fetal insulin-like growth factor–1 (IGF-1) expression is altered in response to maternal dexamethasone administration, this rabbit model of intrauterine growth retardation (IUGR) was utilized. Methods: Eight pregnant rabbits received either dexamethasone (Dex 0.1 mg/kg/d intramuscular), or normal saline (Cont) on gestational days 26 and 27. Fetuses were harvested on gestational day 28 or 29 and were identified as favored (Fav) or runt (Runt): DexFav, DexRunt, ContFav, and ContRunt. Fetal weight was recorded and the serum, amniotic fluid, liver, kidney, and small intestine (SI) were collected. Reverse transcription polymerase chain reaction (RT-PCR) was used to measure IGF-1/β-actin mRNA densitometric band ratios in all tissues. Radioimmunoassay (RIA) was used to measure IGF-1 protein levels in the serum and amniotic fluid. Results: Weight was decreased in the Runt fetuses at all time-points (P