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.
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
V V
VV
Petrov
R H
RH
Fagard
P J
PJ
Lijnen
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