The value of angiotensin-I-converting enzyme determinations in malignant and other diseases.

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.