Improved separation of creatine kinase cardiac isoenzyme in serum by batch fractionation

I describe a simple, single-tube batch fractionation procedure for separating MM and MB isoenzymes of creatine kinase on a macroporous strong anion exchanger (AG MP-1, Bio-Rad Laboratories). The isoenzymes can be separated in less than 3 min, with a resulting dilution of the serum with no more than an equal volume of buffer. Without sample concentration or spectrofluorometric measurement, the procedure detects 4 U of MB isoenzyme per liter. Sensitivity is limited by the sensitivity and precision of the method of measurement. The CV for the fractionation can be held to less than 4.0% at 65 U of MB per liter. Current fractionation methods are compared to the proposed procedure. With use of a discrete analyzer (Du Pont aca) the mean MB activity in a population free of heart disease was 3.2 +/- 3.0 U/liter (range, 0 to 8 U/liter). The kinetics and stability of isolated isoenzymes are reported, indicating that advisability of storing or pre-incubating samples with mercaptoethanol.