Serum and tissue angiotensin converting enzyme in patients with lichen planus.

Serum and tissue angiotensin-converting enzyme (ACE) was measured in 20 patients with lichen planus before and after therapy, and in 20 healthy individuals. Serum and tissue ACE activity was determined by spectrophotometric method using hippuryl-l-histidyl-l-leucine as a substrate. The enzyme activity is expressed in the following units: 1 U corresponds to 1 nmol of hippuric acid released by hydrolysis of hippuryl-l-histidyl-l-leucine per minute and one liter of serum or 50 mg tissue. Before therapy, serum ACE activity was significantly increased in patients with lichen planus (35.9 +/- 2.33 U/L) in comparison to healthy individuals (28.16 +/- 1.7 U/L). Tissue ACE activity was increased in patients with lichen planus (2.24 +/- 0.41 U/50 mg) in comparison to healthy individuals (1.86 +/- 0.16 U/50 mg), but the difference was not significant. After therapy, serum and tissue ACE activity decreased and no significant difference in ACE activity was found. The determination of serum ACE activity may be a good non-specific parameter for the assessment of therapeutic effects.