CHANGES IN SURFACTANT PROTEIN-A MESSENGER-RNA LEVELS IN A RAT MODEL OF INSULIN-TREATED DIABETIC PREGNANCY

Maternal diabetes during pregnancy is associated with increased risk o f neonatal respiratory distress syndrome (RDS). Previous studies using rat models for the diabetic pregnancy have documented decreased amoun ts of surfactant protein mRNA in the lungs of fetuses. In this study, we measured fetal lung surfactant-associated protein A (SP-A) mRNA fro m diabetic rats treated with insulin by daily injection or osmotic pum p. Lungs were taken from fetuses on gestational d 20, and RNA was isol ated and subjected to Northern blotting and densitometry to quantify S P-A mRNA, Fetal lung SP-A mRNA from untreated diabetic pregnancies was 34 +/- 2.9% of control. Insulin treatment increased levels to 55 +/- 4.2% of control values. Fetal lung SP-A mRNA levels were affected by t he timing, length, and effectiveness of insulin treatment. Although le vels from all treatment groups were still less than control values, in sulin treatment during the last 5 or 10 d of pregnancy resulted in a s ubstantial increase in SP-A mRNA levels over those of from untreated d iabetic pregnancies. However, fetuses from the group with insulin trea tment for the entire pregnancy showed decreases in fetal SP-A mRNA lev els. Although the mechanism(s) responsible for the effects of diabetes and its treatment on fetal SP-A expression remain unclear, it appears unlikely that hyperglycemia is the principal cause.