Protein binding of human fetal and maternal plasmas to salicylate.

Abstract

A method is presented that provides a way of studying solute distribution between maternal and fetal plasmas, or between any 2 protein solutions at thermodynamic equilibrium. Using this method, it is shown that a concentration gradient can be established for salicylate between maternal and fetal plasmas reflecting a difference in protein binding by the 2 plasmas independent of a biologic membrane. In addition, the binding properties of human fetal plasma changed during gestation. Finally, the distribution ratios for sodium or chloride concentrations between maternal or fetal plasma and a protein-free solution were the same although the distribution ratios for sodium were distinctly different from those for chloride in undiluted maternal or fetal plasma at physiologic pH.