Relationship between changed alveolar-capillary permeability and angiotensin converting enzyme activity in serum in sarcoidosis.

The effect of altered alveolar-capillary permeability on angiotensin converting enzyme (ACE) activity in serum (SACE) was studied in 45 patients with sarcoidosis and 21 healthy controls. In sarcoidosis increased albumin concentrations in the bronchoalveolar lavage fluid (L albumin) and increased ratios of L albumin to albumin in serum (S albumin) indicated an increased permeability of the alveolar-capillary membrane. ACE activity in the lavage fluid (LACE) was correlated with the number of alveolar macrophages in controls, indicating that it may come from these cells. LACE was high in active sarcoidosis while in inactive disease it was similar to that in controls. SACE in sarcoidosis was significantly increased. Ninety per cent of patients with increased L albumin had increased SACE. SACE activity was significantly correlated with concentrations of L albumin and with LACE activity. The relationships between signs of increased membrane permeability and SACE and between LACE and SACE suggest that excess SACE in sarcoidosis may, at least partly, originate in the alveolar space.