330 EGF DECREASES LUNG GLYCOGEN AND STIMULATES LUNG PHOSPHATIDYLCHOLINE SYNTHESIS IN FETAL RAT

Abstract

We previously demonstrated a relationship between the decrease in the glycogen content of developing rat lung and the appearance of surfactant phospholipids. In the present study we utilize a fetal injection technique to examine the influence of EGF on lung maturation. Our laboratory and others have shown specific binding of EGF to membranes prepared from developing lung. Pregnant rats of 17 to 19 day gestation had uteri exposed by a small lateral suprapubic incision. EGF (10-100 ng) was injected through the uterine wall directly into the amniotic sac of the exposed fetuses. PBS injected fetuses on the centralateral side of the cervex served as controls. Fetal lungs were removed 48 hours later for measurement of glycogen content of lung and for determination of ³H-choline incorporation into phosphatidylcholine. EGF stimulated the incorporation of ³H-choline into phosphatidylcholine by lung slices prepared from fetal rats exposed to intraamniotic EGF from day 17 through 21. A maximal stimulation of 118% was observed in fetuses injected on day 18 and sacrificed on day 20. Lung glycogen content was reduced by 54% in the EGF group. These data provide further support for a relationship between carbohydrate and phospholipid synthesis during lung maturation and provide direct evidence for an EGF influence on fetal lung maturation.

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