Enflurane, halothane and isoflurane do not inhibit angiotensin converting enzyme activity

Area of Science:

• Anesthesiology
• Biochemistry
• Pharmacology

Background:

• Inhalation anesthetics are widely used in surgery.
• Angiotensin converting enzyme (ACE) is a critical component of the renin-angiotensin-aldosterone system, regulating blood pressure.
• The impact of potent inhalation anesthetics on ACE activity remains incompletely understood.

Purpose of the Study:

• To investigate the effects of halothane, enflurane, and isoflurane on the activity of angiotensin converting enzyme (ACE).
• To determine if these anesthetics interfere with the metabolic function of ACE in isolated rabbit lungs.

Main Methods:

• Isolated rabbit lungs were perfused in vitro with a specific substrate ([3H]-benzoyl-phenylalanyl-alanyl-proline, BPAP).
• ACE activity was measured by determining the rate and percentage of BPAP metabolism before and after exposure to anesthetic agents (halothane, enflurane, isoflurane) at four MAC multiples.
• The percentage of BPAP metabolism inhibition was calculated to assess anesthetic effects on ACE activity.

Main Results:

• The average metabolism of BPAP during the control period was 76.5%.
• None of the tested anesthetics (halothane, enflurane, isoflurane) demonstrated significant inhibition of BPAP metabolism.
• The anesthetics did not alter the first-order kinetics of BPAP metabolism, indicating no impact on the fundamental reaction rate.

Conclusions:

• Potent inhalation anesthetics do not directly inhibit angiotensin converting enzyme (ACE) activity in this in vitro model.
• Despite potential alterations to the broader renin-angiotensin-aldosterone axis, these anesthetics do not affect this specific enzymatic step.
• This finding suggests that the direct enzymatic action of ACE is preserved during exposure to halothane, enflurane, and isoflurane.