Delayed pulmonary maturation in the fetus of the streptozotocin-diabetic rat.
Pulmonary maturation was studied in fetuses in streptozotocin-diabetic rats on the final four days of gestation. Diabetes was induced prior to conception by the intravenous injection of streptozotocin. Fetuses were hyperglycemic but did not manifest hyperinsulinemia. Whole lung total phospholipid, phosphatidylcholine, and disaturated phosphatidylcholine were significantly decreased in the diabetic group on day 21 (term = 22 days), but not prior to or after that point in gestation. Morphologic analysis also revealed a decreased number of type II cells and lamellar bodies per alveolar lining cell in the diabetic group only on day 21, coincident with the changes in phospholipid analysis. Activities of enzymes involved in fetal pulmonary phospholipid synthesis were measured to see if differences could account for the observed developmental delay. No significant differences between diabetic and control lungs were noted in any of the enzymes studied from days 20-22, with the exception of an increase in cholinephosphate cytidylyltransferase activity in the diabetic fetuses on day 22. Immaturity in both biochemical and morphologic indices of lung development was present at a specific time late in the diabetic rat gestation. This maturational delay could not be accounted for by changes in the activities of enzymes involved in phospholipid synthesis. The fetus of the streptozotocin-diabetic rat provides a useful model to study the effects of hyperglycemia on fetal lung development.