Angiotensin-converting enzyme in pericardial fluid: comparative study with serum activity.
BACKGROUND
The characterization of an angiotensin-converting enzyme (ACE) in human pericardial fluid is relevant, considering its role in the angiotensin II release and thus, the role of the pericardium in cardiovascular homeostasis.


OBJECTIVE
To isolate and characterize an ACE from human pericardial fluid and to compare the angiotensin I converting activities of the pericardial fluid with that of the serum in patients submitted to cardiovascular surgery.


METHODS
The enzyme from human pericardial fluid was purified through chromatographic steps and characterized by polyacrylamide gel electrophoresis (SDS-PAGE), hydrolysis of angiotensin I, bradykinin, Hip-His-Leu and synthetic substrates with internal fluorescence suppression. Lisinopril was used as inhibitor. The ACE activity was measured in blood and pericardial fluid samples of 23 patients submitted to cardiovascular surgery.


RESULTS
The purified ACE (MM = 140 kDa), releases angiotensin II, hydrolyses bradykinin and the Hip-His-Leu substrate. The kinetic parameters k cat,(s-1) and k cat/Km (microM-1. s-1) were, respectively: Hip-His-Leu (1.14 and 7 x 10 -4) ; Abz-YRK(Dnp)P-OH (2.60 and 0.77), Abz-LFK(Dnp)-OH (2.77 and 0.36) and Abz-SDK(Dnp)P-OH (1.92 and 0.19). The angiotensin I converting activities (mean +/- SD) in the pericardial fluid and in blood, were, respectively: 3.16 +/- 0.90 mU x mg -1x min-1 and 0.33 +/- 0.11 mU x mg -1x min-1. The difference was significant between the two fluids.


CONCLUSIONS
An ACE that bears great similarity with the somatic enzyme was isolated from human pericardial fluid. The angiotensin I converting activity is higher in the pericardial fluid when compared to the serum activity. These data are important evidence of the role of the pericardial fluid in the metabolism of active peptides.
Universidade Federal do Triângulo Mineiro, Uberaba, MG, Brasil. bioq@dcb.uftm.edu.br
Roseli Aparecida da Silva
RA
Gomes
Lívia das Graças Vieito Lombardi
Ld
Teodoro
Isabel Cristina Rezende
IC
Lopes
Patrícia Alessandra
PA
Bersanetti
Adriana Karaoglanovic
AK
Carmona
Valdemar
V
Hial
D002318:Cardiovascular Diseases / Q000097:blood / Q000201:enzymology / Q000601:surgery; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D006868:Hydrolysis; D007703:Peptidyl-Dipeptidase A / Q000097:blood / Q000302:isolation & purification; D010490:Pericardial Effusion / Q000201:enzymology*
D007703:Peptidyl-Dipeptidase A