Solubilization of an angiotensin II binding site from rat liver

The high affinity binding sites for angiotensin II were solubilized from rat liver membranes by treatment with CHAPS. The binding protein was also partially purified by angiotensin III inhibitor-coupled Affi-gel affinity chromatography. Binding to the intact membranes as well as to the solubilized preparation was specific and saturable. According to the Scatchard plot, the membrane preparations exhibited a single class of high affinity binding sites with a Kd of 0.71 nM. The solubilized preparation also showed the presence of a single class of binding sites with less affinity (Kd of 14 nM). Meanwhile the competition studies using angiotensin II analogues represented two separate binding sites for angiotensin II and single binding site for antagonist. These latter findings were correlated to the results provided by Garrison's research group. More works are needed to clarify this discrepancy.