[Modification of the Friedland-Silverstein technic for the determination of the activity of angiotensin I converting enzyme].

The authors studied the parameters of Friedland and Silverstein's technique for measuring the activity of the angiotensin I conversion enzyme and found a number of anomalies. The technique was modified by correcting the wide pH difference between the pH of the reagent and the pH of the reference solution. This modification made the technique optimal for the measurement of the enzyme activity by allowing a 20 to 40 per cent increase in this activity and a 15% increase in the positivity in cases of clinical sarcoidosis. The application of this modified test to the determination of the activity of the angiotension I conversion enzyme in control subjects, patients with sarcoidosis and patients with order respiratory diseases gave the following mean values, respectively: 39 +/- 10 IU; 81 +/- 23 IU; 41.5 +/- 2.5 IU in the serum and 0.2 IU; 1.1 +/- 0.5 IU; 0.2 +/- 0.1 IU in bronchoalveolar lavage fluid. The increase in enzyme activity in sarcoidosis is found in the serum in 75% of cases and in bronchoalveolar lavage fluid in 85% of cases. This modified technique can be applied in routine practice and in research.