The inactivation of bradykinin in the pulmonary circulation of isolated lungs.

1. The isolated lungs of guinea-pigs, rats and dogs, perfused with Krebs bicarbonate solution via the pulmonary artery, inactivated 95, 98 and 99% respectively of the bradykinin infused through them.2. This inactivation process was not inhibited by 2-mercaptoethanol (1 mM) or EDTA (500 muM).3. The inactivation was inhibited by 2:3-dimercaptopropanol (100 muM), N-ethylmaleimide (100 muM), and several of the bradykinin potentiating peptides from Bothrops jararaca, in both natural and synthetic forms.4. The effect of these compounds, 2-mercaptoethanol, EDTA, 2:3-dimercaptopropanol, N-ethylmaleimide and Bothrops peptides on the pulmonary bradykininase activity is the same as their effect on pulmonary angiotensin I converting enzyme.