Dexamethasone-induced histopathology of neonatal rat myocardium.

Dexamethasone-induced relative cardiomegaly in neonatal rats mimics hypertrophic cardiomyopathy seen in premature infants receiving dexamethasone for bronchopulmonary dysplasia. Dexamethasone reduced cellular density by approximately 20%. However, dose related increases in mean fiber diameter were seen and mitotic index was doubled at 12.5 micrograms dexamethasone/injection. In addition, dexamethasone induced collagen accumulation throughout the myocardium in an apparently dose dependent manner. These data suggest that dexamethasone promotes (i) myocardial hypertrophy and possibly hyperplasia and (ii) fibrosis and possibly fibroplasia. Further studies are required to determine relationships between disseminated collagen deposition and other suggested metabolic changes and the observed compensatory myocardial hypertrophy and hyperplasia.