THE BINDING OF THIOCYANATE TO ALBUMIN IN NORMAL HUMAN SERUM AND DEFIBRINATED BLOOD WITH REFERENCE TO THE DETERMINATION OF “THIOCYANATE SPACE” 1

Abstract

The distribution of NaSCN across a cellophane membrane, with normal human serum or blood on one side, was measured. In the concn. range used to determine extravascular "thiocyanate space," approx. a third of total serum thiocyanate is bound to a component of blood which is non-diffusible through cellophane. Comparison of these expts. with work performed on a system containing only water, NaSCN and crystalline human serum albumin demonstrates that it is serum albumin which binds almost all of this thiocyanate, but that a small amt. is bound by another component of serum and red cells. An equation relating free, unbound serum thiocyanate (SCN), to total serum thiocyanate t, and albumin concn. m, (all expressed as moles per kg. water) is [image] Although these results permit a more accurate calculation of "thiocyanate space" than heretofore, the relation of this space to extracellular fluid vol. is uncertain since (1) the concn. of extravascular albumin is unknown, (2) the extent to which thiocyanate enters cells is unknown and (3) equilibrium between thiocyanate in the serum and in the extravascular fluid may not be attained.