The protection of creatine kinase MM sub-bands by EDTA during storage.

We examined the effect of a 5 mmol/l concentration of EDTA on the stabilization of the five serum creatine kinase MM isoenzymes, resolved by thin-layer isoelectric focusing. In patient sera, total CK and CK-MB activities were stable during storage of the samples for two months at 4 degrees C even in the absence of EDTA. However, EDTA stabilized the labile MM and MM1 sub-bands, which are the first to appear in the blood after the release from the damaged tissue and its addition to blood samples intended for determining the MM sub-band pattern is recommended. The stabilizing effect of EDTA was emphasized at higher temperatures. EDTA protected the CK-MM pattern in myocardium extracts made in normal serum and incubated at 37 degrees C during 40 h, but was unnecessary when myocardium was homogenized in heat-inactivated serum. It is thought that EDTA could act by inhibiting a heat-labile component of human serum.