Interrelationship of insulin and somatomedin activity in fetal rats

The effects of glucose and glibenclamide on fetal body weight and fetal serum somatomedin activity were studied. From day 18 to day 20 post-conception, pregnant rats were continuously infused with saline or 40% glucose, which raised the maternal blood sugar to about 200 mg/dl. On day 21 of gestation, fetal body weight was not different, while fetal serum somatomedin activity was significantly elevated in the hyperlycemic animals. Glibenclamide, 1 mg/kg body weight, was injected on day 20 of gestation to the rat mother. The sulfonylurea crossed the placenta. A daily glibenclamide injection from day 16 to day 20 post-conception did not change the fetal body weight, but it significantly augmented the fetal serum somatomedian activity. The results suggest that insulin stimulated the generation of somatomedian activity in the fetus. Both insulin and somatomedian may act as fetal growth factors.