THE HEPATIC RECEPTOR FOR SEX STEROID-BINDING PROTEIN - STUDY ON A NONMALIGNANT CELL-LINE (CHANG LIVER)

The binding of human sex steroid-binding protein (SBP), labelled with I-125, was studied on whole cultured liver (Chang liver cells). SBP wa s shown to bind to a receptor site on normal hepatocytes. The binding was time- and temperature-dependent, highly specific and of high affin ity. The liver receptor recognizing SBP was demonstrated to be differe nt from the asialoglycoprotein receptor; in addition, laminin, which i s structurally related to SBP, could not bind to the receptor. SBP was shown to recognize two binding sites with different affinities; the l ow affinity site was shown to possess a remarkably high capacity. This characteristic, which until now has been described only for hepatocyt es, could be related to the unique role of the liver with regard to bo th SBP and sex steroids.