The Selectivity of the Human Placenta in the Transfer of Plasma Proteins from Mother to Fetus*

Open Access
Publisher Website
Google Scholar
Abstract
Specific human plasma proteins labeled with I131 were injected into pregnant women in the last month of gestation; the thyroids of both mother and fetus were effectively blocked to the uptake of radioiodide by administration of stable iodide. One-hundred and thirty-three women and their respective infants were studied with one of the following proteins: acid glycoprotein, albumin, transferrin, 7S [gamma]2-globulin, fibrinogen, 19S macroglobulin, F fragment from 7S [gamma] 2-globulin, S fragments from 7S [gamma]2-globulin, and 1S to 3S urine [gamma]-globulin ([gamma]u-globulin). The data indicate that: 1) All of the plasma proteins studied appeared in the fetus after administration to the mother but in different amounts. The plasma concentrations of labeled proteins in the fetus relative to those in the mother decreased in approximately the following order: F fragment, a major fraction of S fragments and ru-globulins, 7S [gamma]2-globulin, acid glycoprotein, albumin, transferrin, 19S macroglobulin, and fibrinogen. In some instances, little or no labeled 19S macro-globulin, transferrin, fibrinogen, or even albumin was present in the infant''s plasma at birth. 2) The relative plasma concentrations of F fragment, a major fraction of the S fragments, and the [gamma]u -globulins, which are related immunochemically to the S fragments, were similar to each other, and they were higher than the relative plasma concentrations of 7S [gamma]2-globulin. The problem of translating fetal plasma concentrations of labeled protein into maternofetal transfer rates in the absence of data concerning rates of degradation in the fetus and rates of transfer from fetus to mother is discussed.