Mean values for serum
angiotensin-I-converting enzyme (SACE), determined spectrophotometrically in 648 subjects, using the synthetic substrate
hippuryl-L-histidyl-L-leucine, and expressed in units per milliliter, were: controls, 11.11 +/- 3.97 (n = 89);
lung cancer, 6.50 +/- 3.26 (n = 87);
tuberculosis of the lung, 8.93 +/- 4.60 (n = 68);
pulmonary sarcoidosis, 21.18 +/- 14.93 (n = 48);
pneumonia, 9.81 +/- 6.83 (n = 52);
fibrosis, 11.18 +/- 8.26 (n = 34);
diabetes mellitus, 10.90 +/- 7.51 (n = 29);
ischemic heart disease, 8.98 +/- 6.19 (n = 42);
pulmonary embolism, 13.20 +/- 3.91 (n = 5); and
lymphomas, 11.66 +/- 5.44 (n = 36). The lowest values for SACE (5.92 +/- 1.95) were observed in 7 patients with pulmonary
metastases. No relationship could be found between SACE and other laboratory parameters, nor between the
enzyme activity in men and women. Evidence suggests that low SACE activity is often associated with extrapulmonary
cancers of various organs. Levels were significantly decreased in
cancer of the lung and pulmonary
metastases and significantly (p less than 0.001) increased in
sarcoidosis compared with other diseases, suggesting that SACE activity may be of value in the diagnosis and prognosis of
cancer of the lung.