Angiotensin-converting enzyme in human skeletal muscle. A simple in vitro assay of activity in needle biopsy specimens

Scand J Clin Lab Invest. 1994 Apr;54(2):105-11. doi: 10.3109/00365519409086516.

Abstract

The importance of skeletal muscle for human haemodynamics and metabolism makes it a suitable sample tissue for the measurement of angiotensin converting enzyme (ACE; EC 3.4.15.1). A study of serum and muscle angiotensin-converting enzyme was performed in 50 essential-hypertensive subjects. Muscle tissue was obtained from the vastus lateralis muscle by Bergström needle biopsies. The method used is a modification in Cushman's fluorometric assay for tissue angiotensin-converting enzyme. It utilized 5 mM hippuryl-histidyl-leucine as a synthetic substrate for a 60-min fixed-time incubation at 37 degrees C. The 0.25 ml incubation mixture consisted of 0.12 mM potassium phosphate buffer, pH 8.1, 300 mM NaCl, and 1 or 2 mg homogenized muscle tissue. The activity was found to have the properties previously reported for human ACE. The intra- and interassay coefficients of variation of the method were 13% and 21%, respectively, for the 1 mg incubation as assessed from internal controls (n = 20). the muscle ACE activity in the hypertensive subjects was 49 +/- 14 mU g-1 (mean +/- SD) with no difference between values for men and women. No correlation was found between muscle ACE activity and age, or between muscle and serum angiotensin-converting enzyme activity. We consider this assay a useful new tool for investigating the role of angiotensin-converting enzyme in the pathogenesis and treatment of hypertension, as it can be applied to patient materials.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biopsy, Needle
  • Dipeptides / metabolism
  • Female
  • Fluorometry
  • Fosinopril / pharmacology
  • Humans
  • Hypertension / enzymology*
  • In Vitro Techniques
  • Male
  • Muscles / enzymology*
  • Peptidyl-Dipeptidase A / blood
  • Peptidyl-Dipeptidase A / metabolism*
  • Reproducibility of Results
  • o-Phthalaldehyde

Substances

  • Dipeptides
  • o-Phthalaldehyde
  • histidylleucine
  • Peptidyl-Dipeptidase A
  • Fosinopril