Accelerated Maturation of Fetal Alveolar Epithelium in New Zealand Rabbits After Single Maternal Injections of Solu-Medro
Hyaline membrane disease develops in premature infants as a result of an immature pulmonary epithelium. In utero fetal injections of glucocorticoids accelerate the maturation of the alveolar epithelium. Recent studies indicate that maternal injections of certain glucocorticoids may also be effective. To examine this further, pregnant New Zealand white rabbits were injected (2 mg/kg) with Solu-Medrol (methyl-predisolone) on various days near the end of the gestation period. Two days after injection the fetuses were removed and tissue from the middle portion of the right lobe was processed for electron microscopy. A total of 100 Type I, Type II, and cuboidal cells without inclusions from each fetus was counted. In addition, three morphologically distinct types of osmiophilic inclusions found in the Type II cells were totaled. Using this information, the state of fetal lung maturation was compared in 24 experimental and 12 control fetuses at 24, 26, 28, and 30 days gestation. No significant increase in the number of Type II cells was found, but this might be due to the small size used. The number of Type II cells without inclusions decreased, but the number of Type I cells increased. The number of osmiophilic inclusions in Type II cells was greater in experimental fetuses at 28 and 30 days gestation that in control fetuses. These changes suggest that maternal injections of Solu-Medrol stimulates fetal alveolar maturation.
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