Comparison of two commercially available systems for the electrophoretic separation of alkaline phosphatase isoenzymes

Abstract

Two commercially available electrophoretic methods for the separation of the human serum enzyme alkaline phosphatase (ALP, EC 3.1.3.1) were evaluated: the Isopal system (Beckman, Brea, CA, USA) was compared with the Iso-PAL system (Sebia, Issy-les-amoulineux, France). Both use agarose as supporting medium to separate ALP into its clinically relevant isoenzymes: bone, liver, high- M r (or “fast liver”), intestinal and placental ALP. With both methods, additional fractions for bone, liver and intestinal ALP were found, true isoforms that were called “variant” fractions. The migration pattern differed considerably between the systems, owing to the use of different detergents. Bone and liver ALP were partially separated with both methods. However, when bone ALP exceeded 50% of the total ALP activity, sample treatment was necessary, either with neuraminidase (Beckman) or by applying the sample on a second gel containing wheat-germ lectin to precipitate bone ALP (Sebia). The within-and between-gel reproducibilities of both systems were comparable and remained between 2 and 6% for normal isoenzyme activities. Both systems correlated well, except for high M r ALP. The Sebia system was more sensitive for detecting intestinal ALP, whereas higher liver and bone variant ALP activities were detected with the Beckman system. It is concluded that both methods are convenient for routine use in the clinical laboratory.