Serum angiotensin converting enzyme level in bronchial asthma.

Using hippuryl-L-histidyl-L-leucine as a substrate analogue, serum angiotensin converting enzyme (ACE) was spectrophotometrically estimated in patients with bronchial asthma. The mean level of asthmatic patients was significantly lower than that of the control subjects. The reduced serum ACE activities did not change during an acute asthmatic attack. Significantly lower levels of serum ACE occurred in patients with chronic asthma than in those who only suffered with occasional asthma. Serum ACE activity was not reduced when the patients were taking steroids. Serum ACE activity could not be correlated with either the systolic blood pressure or the diastolic blood pressure of our asthmatic patients. However, serum ACE activity was correlated with the serum beta-globulin fraction in asthmatic patients.