INHIBITION OF ENZYMATIC DEGRADATION OF ANGIOTENSIN-II IN MEMBRANE-BINDING ASSAYS - UTILITY OF 1,10-PHENANTHROLINE

Studies of 125I-labelled angiotensin II binding to membranes from bovine uterus and aorta are rendered impossible because enzymatic degradation of 90% of the added ligand occurs within 30 min at 23°C. High pressure liquid chromatographic analysis has demonstrated that a single iodinated product, which is more hydrophilic than intact angiotensin II, is produced by enzymatic cleavage. Investigation of a series of enzyme inhibitors has shown that the carboxypeptidase inhibitor 1,10-phenanthroline completely inhibits degradation of angiotensin II without disrupting ligand binding.