Somatomedin activity in tracheal fluid from the newborn infant

Tissue and Plasma Somatomedin-C/Insulin-Like Growth Factor I Concentrations in the Human Fetus during the First Half of Gestation

“…The validity of this assumption depends on whether the peptide that can be extracted from a tissue reflects that which might be secreted. The lung appears to be a secretor of Sm-C/ IGF I, since this peptide has been identified in tracheal fluid of human newborns (26).…”

Enteral IGF-I enhances fetal growth and gastrointestinal development in oesophageal ligated fetal sheep

“…With the accompanying increase in amniotic fluid volume, this resulted in a total amniotic fluid IGF-I content approximately 10-fold higher than that of the sham operated control animals. IGF-I enters amniotic fluid from oral and pulmonary secretions (Spencer et al 1983, Hill et al 1984, and from fetal urine. Since failure of clearance by swallowing is likely to apply equally to the saline and IGF-I groups in this experiment, the higher amniotic fluid levels in the IGF-I group suggests increased IGF-I concentrations in fluids entering the amniotic sac.…”

“…Assuming amniotic fluid IGF-I concentrations of 2·5 ng/ml and fetal swallowing rate increasing from 200 ml/day at 90 days to 800 ml/day in late gestation (Harding et al 1984, Tomoda et al 1985, this would equate to the fetus swallowing IGF-I from amniotic fluid at a rate of 0·5 µg/day at 90 days increasing to 2 µg/day at term. However, swallowed fluid not only consists of amniotic fluid but also of pulmonary fluid and naso-oral secretions, both of which contain high levels of IGF-I (Schindler 1982, Hill et al 1984. It has been calculated that 18% swallowed fluid is derived from the fetal ovine lungs (Brace et al 1994).…”