CONCENTRATIONS OF FREE OESTRADIOL, OESTRONE AND OESTRADIOL-PRECURSORS IN HUMAN CORD PLASMA AND FOETAL SYSTEMIC VENOUS PLASMA AT TERM

Abstract

ABSTRACT The concentrations of free oestradiol and oestrone in umbilical venous plasma and in systemic plasma from the newborn have been determined by a double isotope derivative method. The concentration of free oestradiol and oestrone in the umbilical vein is about 7 μg/100 ml plasma and ten times higher than in the newborn. This difference can account for a 24 hours clearance by the foetus of at least 9–15 mg oestrogen. In the same plasma samples, concentrations of oestradiol precursors were determined after in vitro conversion to oestradiol by incubation with a microsomal preparation from human full term placenta. Although a significantly lower precursor concentration was found in umbilical vein plasma than in foetal systemic venous plasma, the difference was much too small to account for the oestrogen production in the placenta.