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Angiotensin-converting enzyme determination in plasma during therapy with converting enzyme inhibitor: two methods
1Department of Chemical Pathology, St. Vincent's Hospital, Fitzroy, Victoria, Australia.
Clinical Chemistry
|August 1, 1991
Summary
The fluorometric assay using hippuryl-histidyl-leucine (HHL) is less reliable than the spectrophotometric assay with 3-(2-furylacryloyl)-L-phenylalanyl-glycyl-glycine (FAPGG) for measuring angiotensin-converting enzyme (ACE) inhibition during therapy. The FAPGG method accurately reflects in vivo ACE activity changes.
Area of Science:
- Biochemistry
- Pharmacology
- Clinical Chemistry
Background:
- Plasma angiotensin-converting enzyme (ACE) activity is crucial for blood pressure regulation.
- ACE inhibitors (CEIs) are widely used to manage cardiovascular conditions.
- Accurate measurement of ACE inhibition is essential for effective CEI therapy.
Purpose of the Study:
- To compare the reliability of two methods for measuring plasma ACE activity in patients receiving CEI therapy.
- To determine which assay accurately reflects in vivo ACE inhibition.
Main Methods:
- Plasma ACE activity was measured using a manual fluorometric method (HHL substrate) and an automated spectrophotometric method (FAPGG substrate).
- Plasma concentrations of angiotensin I (ANG I) and angiotensin II (ANG II) were measured in patients receiving perindopril.
- The ratio of ANG II:ANG I was used as an index of in vivo ACE activity.
Main Results:
- Both methods correlated well for normal ACE activity.
- The spectrophotometric method (FAPGG) showed greater suppression of ACE activity than the fluorometric method (HHL) in patients on CEI therapy.
- Changes in the ANG II:ANG I ratio during perindopril therapy closely agreed with ACE activity measured by the FAPGG method, but not the HHL method.
Conclusions:
- Measurement of plasma ACE activity using FAPGG substrate provides a reliable assessment of in vivo ACE inhibition during CEI therapy.
- The HHL method may underestimate the efficacy of CEIs.
- The FAPGG assay is recommended for monitoring ACE inhibition in patients on CEI therapy.