ABSTRACT
Neutral endopeptidase (neprilysin; EC 3.4.24.11) is present in the brush border membrane, for example in the bile ducts. We investigated serum neprilysin activity and its correlation with cholestatic markers in patients with primary biliary cirrhosis. Sera of 39 patients with primary biliary cirrhosis (37 females, 2 males, mean age 45 years, range 24-71 years) were investigated. Twenty-seven healthy volunteer subjects served as control. Serum neprilysin activity was measured by a sensitive microplate-based continuous monitoring kinetic assay. Succinyl-alanyl-alanyl-phenyl-alanyl-4- nitroanilide was used as substrate. For statistical analysis Kruskal-Wallis ANOVA by ranks and Mann-Whitney U test were used. The neprilysin activities were significantly higher in stages III (mean 13.2 +/- SD 10.8 U/l) and IV (21.8 +/- 17.5) than in the control subjects (2.4 +/- 2.9, p < 0.01). There was no significant difference in neprilysin activity between the patients with stages I and II, or between stage I + II (2.88 +/- 3.0) and the control. Positive correlation was found between the activity of neprilysin and serum bilirubin, alkaline-phosphatase and gamma-glutamyl-transferase (p < 0.005 for each). In this study we confirmed that serum neprilysin activity is elevated in patients with primary biliary cirrhosis at advanced stages and the elevation correlated with the cholestatic markers. The increased neprilysin activity seems to be an indicator for the severity and progression of the disease.
Subject(s)
Liver Cirrhosis, Biliary/enzymology , Neprilysin/blood , Adult , Aged , Alanine Transaminase/blood , Alkaline Phosphatase/blood , Aspartate Aminotransferases/blood , Bilirubin/blood , Biomarkers/blood , Case-Control Studies , Disease Progression , Female , Humans , Liver Cirrhosis, Biliary/blood , Male , Middle Aged , Severity of Illness Index , gamma-Glutamyltransferase/bloodABSTRACT
A sensitive microplate-based continuous monitoring (kinetic) assay is described for the determination of serum neutral endopeptidase (EC 3.4.24.11) activity. The relatively simple technique is suitable for routine and serial measurements of neutral endopeptidase activity in human serum and other body fluids using a kinetic microplate reader. In 38 healthy blood donors (27 males, 11 females, age range 19-51 years) the mean activity of the enzyme was 3.43 +/- 1.02 U/l. The activities did not differ between sexes (P = 0.895, N.S.).
