Dexamethasone Administration to Newborn Mice Alters Mucosal and Muscular Morphology in the Ileum and Modulates IGF-I Localization

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Abstract
Glucocorticoid exposure accelerates the maturation of small bowel mucosa. We hypothesized that IGF-I, a mitogen and differentiating peptide expressed in small bowel, mediates steroid-induced change within the developing ileum. To investigate this possibility, we intraperitoneally administered 1 μg/gm/d of dexamethasone (DEX) or equal volumes of saline to litter-mate newborn mice. The animals were killed on d 1–3 of life and their ileums were harvested and prepared for microscopy. Tissue sections of ileum were examined for morphologic analyses, mucin staining, immunolocalization of IGF-I and -II, proliferating cell nuclear antigen (PCNA), terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and in situ hybridization for IGF-I transcripts.