Arginine-aminopeptidase in rat cardiac fibroblastic cells participates in angiotensin peptide turnover.
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.
Petrov
V V
VV
Hypertension and Cardiovascular Rehabilitation Unit, Campus Gasthuisberg, Department of Molecular and Cardiovascular Research, University of Leuven (KULeuven), Herestraat 49, Louvain 3000, Belgium. victor.petrov@med.kuleuven.ac.be
Fagard
R H
RH
Lijnen
P J
PJ
D000626:Aminopeptidases / Q000032:analysis / Q000378:metabolism*; D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000378:metabolism*; D006868:Hydrolysis; D015151:Immunoblotting / Q000379:methods; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D016212:Transforming Growth Factor beta; D000804:Angiotensin II; D001120:Arginine; D000626:Aminopeptidases; C019721:aminopeptidase B