Determination of fetal lung maturity in rats by fluorescence polarization

The fluorescence polarization technique was utilized to determine fetal lung maturity in rats. The study confirmed that changes in fluorescence polarization values with gestational age follow the pattern already seen in human beings. A sharp drop was observed on the afternoon of the 20th day of gestation which corresponds in the rat to the beginning of surfactant synthesis. This was confirmed by determination of phosphatidylglycerol. In order to verify the effectiveness of this animal model, a group of pregnant rats was treated with 100 micrograms/kg betametasone twice 48 and 24 hr before the 20th or 21st days of gestation. As expected, this significantly reduced fluorescence polarization on day 20 (4-6 p.m.) and day 21 of gestation, indicating increased surfactant synthesis in betametasone-treated rats. Another group of female rats was pretreated before mating with streptozotocin (40 mg/kd), inducing diabetes. Fluorescence polarization values in the amniotic fluid of the diabetic rats at the above intervals were significantly higher than controls, indicating reduced lung maturation.