A comparison of insulin receptors in the developing fetal lung in normal and in streptozotocin-induced diabetic pregnancies.

Insulin receptors from fetal rat lungs of normal and streptozotocin-induced diabetic pregnancies were examined for their binding capacities and association constants. Sprague-Dawley rats, given a single dose of streptozotocin at 7 days' gestation, became hypoinsulinemic and hyperglycemic within 48 hours, although they remained healthy enough to carry fetuses to term. The fetuses of the streptozotocin-treated pregnancies had hyperglycemia (3,750 +/- 400 micrograms glucose/ml vs 390 +/- glucose/ml for control subjects), but were not hyperinsulinemic. Insulin receptor binding capacities of fetal lungs from control pregnancies increased as a function of gestational age from 16 to 21 days. Receptor binding capacities of lungs from streptozotocin-treated pregnancies also increased with gestational age until 21 days, when they dropped to 50% of control values. It was demonstrated in organ culture that fetal lung receptors from normal pregnancies of 20 days' gestation could be down-regulated in the presence of insulin and that this down-regulation is coupled to a biologic effect of insulin, hexose transport. It was concluded that fetal lung insulin receptors can be regulated by insulin concentrations in vitro and by experimental diabetic pregnancies in vivo.