The additivity principle in the reaction of angiotensin II and its analogs with antibodies and receptors of glomerular cells from the rat adrenal cortex

The binding of angiotensin II and its analogues (13) to rabbit antibodies and glomerular cell receptors from rat adrenal cortex was studied, using the radioimmunoassay method and radioreceptor analysis. Double modifications introduced into the angiotensin structure were found to increase in an additive fashion its binding to the antibodies and renal cell receptors. The relative binding activity of the analogues carrying a double modification can be assessed if the activities of the analogues with the appropriate single modifications are known. It was concluded that the testing of modifications in the peptide structure for their additivity may provide some insight into the conformational properties of peptides during their binding to the protein.