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  • Title: Arginine-aminopeptidase in rat cardiac fibroblastic cells participates in angiotensin peptide turnover.
    Author: Petrov VV, Fagard RH, Lijnen PJ.
    Journal: Cardiovasc Res; 2004 Mar 01; 61(4):724-35. PubMed ID: 14985069.
    Abstract:
    OBJECTIVE: The aim of the present study was to elucidate the presence in rat cardiac fibroblastic cells of arginine-aminopeptidase and its involvement in the hydrolysis of angiotensin peptides. METHODS: Peptidase activity was measured as hydrolysis of the synthetic substrates, aryl-p-nitroanilides. Immunoblottings were performed with antibodies to aminopeptidase B and Glyceraldehyde-3-phosphate dehydrogenase. RESULTS: Arginine-aminopeptidase found in cardiac fibroblasts (Fb) was arginine and lysine specific, sensitive to various aminopeptidase (AP) inhibitors and to the inhibitor of metalloproteases, 1.10-phenatroline. Experiments with arphamenine A, a specific inhibitor of aminopeptidase B, have shown the presence of two Arginine-aminopeptidase activities: arphamenine-sensitive: chloride-stimulated Arginine-aminopeptidase, and arphamenine-insensitive: chloride-insensitive Arginine-aminopeptidase. Transforming growth factor-beta1 stimulated both Arginine-aminopeptidase activities by approximately threefold. Immunoblot with an antibody specific to rat aminopeptidase B has revealed that arphamenine-sensitive: chloride stimulated aminopeptidase is aminopeptidase B. Arginine-p-nitroanilide hydrolysis was significantly inhibited by angiotensin peptides such as angiotensin (1-10), (1-8), (1-7), (1-4), (5-8), (4-8), (3-8), and (2-8) at the concentration of 50 micromol/l which was fourfold less than the Arginine-p-nitroanilide concentration. CONCLUSIONS: Our data show that chloride-insensitive Arginine-aminopeptidase could contribute to the hydrolysis of all studied angiotensin peptides in concert with other peptidases present in fibroblasts. Some of the peptides could probably not be hydrolyzed by Arginine-aminopeptidase. Instead, they could be first hydrolyzed by another peptidase in fibroblasts and the product of this hydrolysis could be a substrate for Arginine-aminopeptidase. The data obtained suggest that Arginine-aminopeptidase could perform processing of angiotensin peptides in the myocardium and participate in processes regulated by angiotensins such as fibrosis.
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