Enzima conversora de angiotensina no líquido pericárdico: estudo comparativo com a atividade sérica / Angiotensin-converting enzyme in pericardial fluid: comparative study with serum activity

FUNDAMENTO: A caracterização de uma enzima conversora de angiotensina (ECA) no líquido pericárdico humano é relevante diante do seu papel na liberação de angiotensina II e, portanto, do papel do pericárdio na homeostase cardivascular. OBJETIVO: Isolar e caracterizar uma ECA do líquido pericárdico humano. Comparar as atividades conversoras de angiotensina I do fluido pericárdico e do soro de pacientes submetidos à cirurgia cardiovascular. MÉTODOS: A enzima do líquido pericárdico humano foi purificada por meio de etapas cromatográficas e caracterizada por eletroforese em gel de poliacrilamida (SDS-PAGE), hidrólise de angiotensina I, bradicinina, Hip-His-Leu e substratos sintéticos com supressão interna de fluorescência. Lisinopril foi usado como inibidor. A atividade de ECA foi determinada em amostras de sangue e líquido pericárdico de 23 pacientes submetidos à cirurgia cardiovascular. RESULTADOS: A ECA purificada (MM = 140 kDa) libera angiotensina II, hidrolisa a bradicinina e o substrato Hip-His-Leu. Os parâmetros cinéticos k cat,(s-1) e k cat/Km (µM-1. s-1) foram respectivamente: Hip-His-Leu (1,14 e 7 x 10 -4), Abz-YRK(Dnp)P-OH (2,60 e 0,77), Abz-LFK(Dnp)-OH (2,77 e 0,36) e Abz-SDK(Dnp)P-OH (1,92 e 0,19). As atividades conversoras de angiotensina I (média ± DP) do líquido pericárdico e no soro foram, respectivamente, 3,16 ± 0,90 mU x mg -1x min-1 e 0,33 ± 0,11 mU x mg -1x min-1 . A diferença foi significativa entre os dois fluidos. CONCLUSÃO: Uma ECA com grande similaridade com a enzima somática foi isolada do fluido pericárdico humano. A atividade conversora de angiotensina I é maior no líquido pericárdico quando comparada com a atividade do soro. Esses dados constituem importante evidência do papel do líquido pericárdico no metabolismo de peptídeos ativos.

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 (µM-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. CONCLUSION: 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.

Association of urinary 90 kDa angiotensin- converting enzyme with family history of hypertension and endothelial function in normotensive individuals

We described angiotensin-I-converting enzyme (ACE) isoforms with molecular masses of 190, 90, and 65 kDa in the urine of normotensive offspring of hypertensive subjects. Since they did not appear in equal amounts, we suggested that 90 kDa ACE might be a marker for hypertension. We evaluated the endothelial response in normotensive offspring with or without family history of hypertension and its association with the 90 kDa ACE in urine. Thirty-five normotensive subjects with a known family history of hypertension and 20 subjects without a family history of hypertension, matched for age, sex, body weight, and blood pressure, were included in the study. Endothelial function was assessed by ultrasound and a sample of urine was collected for determination of ACE isoforms. In the presence of a family history of hypertension and detection of 90 kDa ACE, we noted a maximal flow mediated dilation of 12.1 ± 5.0 vs 16.1 ± 6.0 percent in those without a previous history of hypertension and lacking urinary 90 kDa ACE (P < 0.05). In subjects with a family history of hypertension and presenting 90 kDa ACE, there were lower levels of HDL-cholesterol (P < 0.05) and higher levels of triglycerides (P < 0.05). Subjects with 90 kDa ACE irrespective of hypertensive history presented a trend for higher levels of triglycerides and HDL-cholesterol (P = 0.06) compared to subjects without 90 kDa ACE. Our data suggest that the 90 kDa ACE may be a marker for hypertension which may be related to the development of early atherosclerotic changes.

Angiotensin converting enzyme from sheep mammary, lingual and other tissues.

Occurrence of angiotensin converting enzyme (ACE) in mammary gland and tongue taste epithelium was demonstrated for the first time. Six times higher ACE activity in lactating mammary gland, than non-lactating mammary gland, suggested pregnancy and lactation hormonal dependent expression of ACE in female mammals. ACE activity was highest in choroid plexus, less in spinal cord and moderate in cerebrum, medulla, cerebellum and pons. Distribution of ACE in different regions of skin, kidney and among other tissues was different. Presence of ACE in adrenal glands, pancreas, bone marrow and thyroid gland indicated functions other than blood pressure homeostasis for this enzyme.