Effect of chloride and diamide on serum angiotensin I-converting enzyme activity from eight mammalian species.

1. The effect of chloride on serum angiotensin I-converting enzyme (ACE) activity was characterized in eight mammalian species: dog, guinea pig, hamster, human, mouse, rabbit, rat, and sheep. 2. Optimum chloride concentrations varied from 300 mM for rabbit to 1700 mM for hamster. 3. The increments with these optimum concentrations with respect to 100 mM chloride concentration were from 1.4-fold in rabbit to 7.9-fold in hamster and dog. 4. There was no correlation between serum chloride concentration or serum ACE activity and optimum chloride concentration. 5. Serum ACE increased only in humans with diamide pretreatment suggesting the presence of endogenous inhibitors.