EFFECT OF MATERNAL DEXAMETHASONE TREATMENT ON FETAL LUNG VITAMIN-A STORES IN THE PERINATAL RAT

Vitamin A (retinol) is essential for normal differentiation of develop ing respiratory epithelium. Significant vitamin A storage occurs in th e fetal lung near term (gestational day 21) in the perinatal rat, and the developing lung may be dependent on these local vitamin A stores d uring growth and differentiation. The growth and differentiation of fe tal lungs can be enhanced by maternal treatment with glucocorticostero ids. We conducted this study in rats to determine the effect of matern al dexamethasone treatment on the lung stores of vitamin A in the offs pring. Vitamin A-sufficient pregnant rats were given by intraperitonea l injection a single dose of either dexamethasone (300 mug) or 0.9% pe rsaline solution on gestational day 16. High performance liquid chroma tography was used to measure concentrations of vitamin A and its ester s, retinyl palmitate and stearate, in fetal and neonatal lungs and liv ers at times ranging from gestational day 19 through 21, and from post natal day 1 through 7. The concentrations of vitamin A esters in the l ungs of fetuses and newborn pups of the dexamethasone-treated animals were significantly lower than those of the control group in all determ inations, the values ranging between 22 and 50% of controls. In contra st, the concentrations of vitamin A esters in the livers did not diffe r significantly between study groups. We conclude that a prompt, susta ined, and selective decrease in the fetal lung stores of vitamin A app ears to occur following maternal antenatal dexamethasone treatment. Th is decrease in the fetal lung vitamin A stores might be due to increas ed utilization of vitamin A associated with enhanced differentiation o f the fetal lung induced by maternal dexamethasone treatment. The poss ibility that glucocorticosteroid treatment in human mothers with immin ent preterm deliveries might alter the lung vitamin A stores of their newborn infants at birth deserves attention.