Yoji Marui

Rapid analysis of serum lactate dehydrogenase isoenzymes by high-performance ion-exchange chromatography

Abstract The repetitive analysis of serum lactate dehydrogenase (LDH) isoenzymes has been performed on a weak anion exchanger (TSKgel DEAE-5PW), which was developed by introducing diethylaminoethyl groups into TSKgel G5000PW (10 μm particle diameter) — a hydrophilic polymer-based material of large pore size — for high-performance gel chromatography. By use of this anion exchanger, a high-pH (8.0) solvent could be used and the albumin peak was completely separate from the LDH isoenzyme peaks. After 10 successive analyses with an autosampler, the coefficient of variation of the LDH isoenzyme elution times was ⩽ 0.90%, and the coefficient of variation for peak areas was ⩽ 3.85%. After 40 successive analyses, resolution between isoenzymes was generally 1.25. This column can be used for more than 300 intermittent injections of human serum.

Multi-enzyme reference material from established human cell lines and human sources

A multi-enzyme reference material was prepared from seven enzymes of asparatate aminotransferase (AST, EC 2.6.1.1), alanine aminotransferase (ALT, EC 2.6.1.2), alkaline phosphatase (ALP, EC 3.1.3.1), lactate dehydrogenase (LD, EC 1.1.1.27), creatine kinase (CK, EC 2.7.2.2), gamma-glutamyltranspeptidase (gamma-GT, EC 2.3.2.2) and amylase (AMY, EC 3.2.1.1) which were purified from human sources including established human cell lines. The enzymatic properties of the material closely resembled those of human serum. In lyophilized form the preparation was stable for at least 200 days when stored at 40 degrees C. Intermethod comparisons of the enzyme activities in 80 clinical specimens were done by correcting the mean values with calibration constants for different assay methods resulting from use of a human serum, the multi-enzyme reference and a commercial control serum. The results from the comparison for the six enzymes of AST, ALT, LD, CK, gamma-GT and AMY in use of the multi-enzyme reference were almost the same as those with use of a human serum as a calibrator, but were not satisfactory for ALP. Even though further search for more reliable material for ALP is required the multi-enzyme reference material can be used for standardization in clinical chemistry.