HEMORPHINS INHIBIT ANGIOTENSIN-IV BINDING AND INTERACT WITH AMINOPEPTIDASE-N

[I-125]-Ang IV binding to rabbit collecting duct cell membranes was in hibited by hemorphins (H), a class of endogenous peptides obtained by hydrolysis of the beta chain of hemoglobin. The most potent competitor s were those with a valine in their N-terminal part such as LVV-H7 and VV-H7 (IC50 = 1.3 nM) followed by VV-H8 and (KVV)-V-6-H7 (5.1 nM). Th e same H, like Ang IV, interacted with aminopeptidase N (APN) as shown by their inhibitory effect (28-36%) on APN activity. HPLC analysis sh owed that only H with a N-terminal valine or leucine were hydrolyzed. Since H are detected in the body fluids, they are likely to act as end ogenous competitors of Ang N. (C) 1998 Elsevier Science Inc.