Production of insulin-like growth factor binding protein(s) (IGF-BPs) by human placenta: variation with gestational age.

Preterm human placentae produce insulin-like growth factor- (IGF-)specific binding protein(s). Competitive binding experiments revealed at least two distinct, high-affinity binding sites for IGF-I and IGF-II. Gel permeation chromatography and sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of the binding protein(s) suggested that they possess a molecular weight in the 45 to 50 kD range. In contrast, term placental tissue produced almost no detectable binding protein activity.