Angio convert enzyme blood test
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Angiotensin-Converting Enzyme (ACE) Blood Test: Methods and Applications
Introduction to Angiotensin-Converting Enzyme (ACE) Blood Test
The angiotensin-converting enzyme (ACE) blood test is a diagnostic tool used to measure the activity of ACE in the blood. ACE plays a crucial role in blood pressure regulation and electrolyte balance by converting angiotensin I to the potent vasoconstrictor angiotensin II. This test is particularly useful in diagnosing and managing conditions such as sarcoidosis and hypertension.
High-Performance Liquid Chromatography (HPLC) for ACE Activity
Methodology and Application
High-performance liquid chromatography (HPLC) is a sophisticated method used to determine ACE activity in biological samples. The process involves incubating samples with hippurylhistidylleucine, an artificial substrate of ACE. The reaction is terminated with metaphosphoric acid, and the liberated hippuric acid is quantified using reversed-phase HPLC. This method allows for the determination of ACE activity in whole blood and various tissues, showing significant variation across different species.
Automated Kinetic Assay for ACE in Serum
Development and Validation
An automated kinetic method for measuring ACE activity in serum has been developed and validated. This method uses N-[3-(2-furyl)-acryloyl]-L-phenylalanylglycylglycine as a substrate and has been adapted for use on the Olli C + D analyzer. The assay has been shown to be reliable, with established normal reference intervals for different populations, including adults, newborns, women on oral contraceptives, smokers, and patients with sarcoidosis.
Colorimetric Assays for ACE Activity
Sensitive Colorimetric Procedure
A sensitive colorimetric assay for ACE activity in serum involves incubating serum with hippuryl-glycyl-glycine and then derivatizing the liberated glycyl-glycine with trinitrobenzenesulfonate. The absorbance is measured at 420 nm, providing a linear range up to 900 U/L and a detection limit of less than 4 U/L. This method demonstrates good precision and correlates well with HPLC results.
High-Throughput Colorimetric Assay
A high-throughput colorimetric assay has been developed to measure ACE activity by quantifying the released hippuric acid from hippuryl-histidyl-leucine. This method is comparable to the standard HPLC method and is suitable for screening ACE inhibitors in a 96-well microplate format, making it a powerful tool for high-throughput applications.
Fluorimetric and Radioassay Methods
Fluorimetric Assay
A fluorimetric assay for ACE activity in serum uses the substrate analog hippuryl-L-histidyl-L-leucine, which is converted to hippurate and L-histidyl-L-leucine. The products are quantified spectrofluorimetrically, providing a sensitive and reproducible method for diagnosing and managing conditions like sarcoidosis.
Radioassay
A radioassay method measures ACE activity by the rate of release of 3H-labelled hippurate from p-[3H]benzoylglycylglycylglycine. This method is specific and provides results within 1.5 hours, although potential interference from unrecognized enzymes in abnormal sera must be considered.
Conclusion
The ACE blood test is a versatile diagnostic tool with various methods available for measuring ACE activity, including HPLC, automated kinetic assays, colorimetric assays, fluorimetric assays, and radioassays. Each method has its advantages and specific applications, making it possible to choose the most appropriate technique based on the clinical context and available resources. These tests are essential for diagnosing and managing conditions such as sarcoidosis and hypertension, contributing significantly to patient care.
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