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Modulation of converting enzyme activity by hypoxia and its physiological effects
Ciba Foundation Symposium
|January 1, 1980
Summary
Acute alveolar hypoxia reduces converting enzyme activity, lowering angiotensin II levels. This impacts blood pressure differently based on bradykinin infusion, revealing oxygen
Area of Science:
- Cardiovascular Physiology
- Respiratory Physiology
- Renal Physiology
Background:
- Converting enzyme activity is crucial in regulating blood pressure via the renin-angiotensin-aldosterone system.
- Acute alveolar hypoxia is known to affect cardiovascular parameters, but its precise impact on converting enzyme activity and related peptides remains to be fully elucidated.
Purpose of the Study:
- To investigate the haemodynamic effects of reduced converting enzyme activity induced by acute alveolar hypoxia.
- To determine the role of oxygen tension in regulating circulating levels of angiotensin II and bradykinin.
Main Methods:
- Sequential haemodynamic measurements were performed in anaesthetized, catheterized dogs.
- Dogs were ventilated with room air, followed by hypoxic gas mixtures, with or without bradykinin infusion.
- Converting enzyme activity, arterial angiotensin II, and bradykinin concentrations were measured.
Main Results:
- Hypoxia rapidly decreased converting enzyme activity and arterial angiotensin II levels.
- Bradykinin-infused dogs showed decreased systemic vascular resistance and increased cardiac output, unlike control dogs.
- Oxygen tension was identified as a regulator of converting enzyme activity and circulating angiotensin II and bradykinin.
Conclusions:
- Acute alveolar hypoxia significantly alters haemodynamics by modulating converting enzyme activity.
- The study highlights the differential haemodynamic responses to hypoxia, influenced by bradykinin levels.
- Oxygen tension plays a key role in regulating the balance between angiotensin II and bradykinin.