Angiotensin converting enzyme (ACE) participates in the renin cascade in response to hypovolemia, by converting angiotensinogen I to angiotensinogen II. The latter hormone is a potent vasoconstrictor that increases blood pressure.
The endothelium of the lung is the primary source of ACE. Because of this location, ACE production is increased in sarcoidosis, which is a granulomatous disease the affects the lungs. Serum ACE concentration is elevated in 79% of patients with active sarcoidosis. ACE activity reflects disease activity. Levels are higher in stage III than in stage 1 disease. Enzyme activity decreases dramatically in some patients after prednisone therapy.
Other diseases such as Gaucher’s disease, leprosy, histoplasmosis, amyloidosis, untreated hyperthyroidism, psoriasis and chronic renal disease have also been associated with increased ACE levels. Serum ACE is significantly decreased in patients taking ACE inhibitors such as Vasotec and captopril. Corticosteroids may slightly decrease ACE values.
Adult reference range is 16-85 U/L. Healthy children and adolescents have values that are 20% to 50% higher than adults.
Specimen requirement is one red top or SST tube of blood. Lavender top tubes should not be used because EDTA inhibits the enzyme.
References
Liebermann J: Elevation of serum angiotensin-converting-enzyme (ACE) level in sarcoidosis. Am J Med. 1975;59:365-372.
Rodriguez GE, Shin BC, Abernathy RS, Kendig EL Jr: Serum angiotensin-converting enzyme activity in normal children and in those with sarcoidosis. J Pediatr. 1981;99:68-72
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