Key result
In heart failure patients on ACE inhibitors, angiotensin-(1-9) levels remained low (1-2 fmol/ml) despite a >40-fold increase in angiotensin I, indicating little role for ACE2 in its metabolism.
Why the study?
Does ACE2 play a major role in angiotensin peptide metabolism in the human coronary circulation?
Observational
Does ACE2 play a major role in angiotensin peptide metabolism in the human coronary circulation?
ACE2 appears to have little role in angiotensin I metabolism in the human coronary circulation, as angiotensin-(1-9) levels do not increase in response to elevated angiotensin I.
ACE2 contributes minimally to coronary angiotensin I metabolism in HF on ACE inhibitors; this Level 3 evidence leaves open its role elsewhere or with targeted therapies.
OBJECTIVE: To investigate the role of angiotensin-converting enzyme-related carboxypeptidase (ACE2) in angiotensin peptide metabolism in the human coronary circulation. METHODS: Angiotensin I and angiotensin II, and their respective carboxypeptidase metabolites, angiotensin-(1-9) and angiotensin-(1-7), were measured in arterial and coronary sinus blood of heart failure subjects receiving angiotensin-converting enzyme (ACE) inhibitor therapy and in normal subjects not receiving ACE inhibitor therapy. In addition, angiotensin I, angiotensin II and angiotensin-(1-7) were measured in arterial and coronary sinus blood of subjects with coronary artery disease before, and at 2, 5 and 10 min after, intravenous administration of ACE inhibitor. RESULTS: In comparison with normal subjects, heart failure subjects receiving ACE inhibitor therapy had a greater than 40-fold increase in angiotensin I levels, but angiotensin-(1-9) levels were low (1-2 fmol/ml), and similar to those of normal subjects. Moreover, angiotensin-(1-7) levels increased in parallel with angiotensin I levels and the angiotensin-(1-7)/angiotensin II ratio increased by 7.5-fold in coronary sinus blood. Intravenous administration of ACE inhibitor to subjects with coronary artery disease rapidly decreased angiotensin II levels by 54-58% and increased angiotensin I levels by 2.4- to 2.8-fold, but did not alter angiotensin-(1-7) levels or net angiotensin-(1-7) production across the myocardial vascular bed. CONCLUSIONS: The failure of angiotensin-(1-9) levels to increase in response to increased angiotensin I levels indicated little role for ACE2 in angiotensin I metabolism. Additionally, the levels of angiotensin-(1-7) were more linked to those of angiotensin I than angiotensin II, consistent with its formation by endopeptidase-mediated metabolism of angiotensin I, rather than by ACE2-mediated metabolism of angiotensin II.
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Campbell et al. (2004) conducted an observational in Heart failure and coronary artery disease. ACE inhibitor vs. Normal subjects / baseline was evaluated on Angiotensin peptide levels in arterial and coronary sinus blood. In heart failure patients on ACE inhibitors, angiotensin-(1-9) levels remained low (1-2 fmol/ml) despite a >40-fold increase in angiotensin I, indicating little role for ACE2 in its metabolism.
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