Endogenous Aminopeptidase N Decreases the Potency of Peptide Agonists and Antagonists of the Kinin B₁Receptors in the Rabbit Aorta

Abstract

The B 1 receptor for kinins is selectively stimulated by bradykinin-related fragments lacking the C-terminal arginine, des-arginine 9 -bradykinin (des-Arg 9 -BK), and Lys-des-Arg 9 -BK. The latter peptide is the optimal agonist at the human and rabbit receptor. The B 1 receptor is inducible as a function of inflammatory conditions in the vasculature. We studied the effect of endogenously expressed peptidases on the potency of ligands of this receptor in an established bioassay, the rabbit aorta contractility. The potency measured for agonists (EC 50 ) or antagonists (pA 2 scale) in this assay was compared with the affinity of each agent determined using

Cooperative effects of aminopeptidase N (CD13) expressed by nonmalignant and cancer cells within the tumor microenvironment

“…Identification of APN substrates implicated in tumor growth and metastasis is another required next step. A number of cytokines, growth factors, and extracellular matrix molecules implicated in angiogenesis have been reported as putative APN substrates (46)(47)(48)(49)(50)(51)(52)(53)(54)(55), and testing their possible roles in the models presented here will be the focus of future studies.…”

A ligand-based approach to investigate the expression and function of angiotensin converting enzyme in intact human umbilical vein endothelial cells

“…2A). The des-Arg 9 -kinins that are B 1 receptor agonists exhibit only very little capacity to compete for [ 3 H]enalaprilat in the applied assay, although ACE is a significant but slow and nonexclusive degradation pathway for these peptides in various physiological settings [7,11]. The binding site differs from the BK B 2 receptor by the low or null affinity of ligands that have been designed to resist to inactivation (the agonist B-9972 and the nonpeptide antagonist LF 16-0687, Fig.…”

Vascular smooth muscle contractility assays for inflammatory and immunological mediators

“…The peptide antagonist of the bradykinin B 1 receptor Lys-[Leu 8 ]des-Arg 9 -braykinin is susceptible to aminopeptidase N inactivation in the rabbit isolated aorta because it is considerably more potent in the presence of the aminopeptidase inhibitor amastatin ( fig. 7B-D) [67]. This did not apply to the agonist used in this series of experiments, des-Arg 9 -bradykinin, but the alternate high affinity agonist Lys-desArg 9 -bradykinin was also susceptible to potency distortion by the action of aminopeptidase N [67].…”

“…The compact structure of the contractile tissue, like the rabbit aorta which contains about 25 layers of smooth muscle cells along with elastic laminae and other conjunctive tissue ( fig. 7, top right) [67], is the physical basis of diffusion barriers that will support the lack of equilibrium between the drug concentrations in the bathing fluid and that at the receptor level,…”