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

Area of Science:

• Biochemistry
• Clinical Chemistry
• Enzymology

Background:

• Creatine kinase (CK) is a key enzyme in energy metabolism, particularly in muscle and brain tissue.
• CK exists in different isoenzyme forms, including creatine kinase MM (CK-MM), which has distinct sub-bands (MM1, MM2, MM3).
• The stability of CK-MM sub-bands is critical for accurate diagnostic interpretation, as they can be affected by sample handling and storage.

Purpose of the Study:

• To investigate the stabilizing effect of ethylenediaminetetraacetic acid (EDTA) on serum creatine kinase MM isoenzymes.
• To determine the optimal conditions for preserving the CK-MM sub-band pattern in patient samples.

Main Methods:

• Serum samples were analyzed for total CK and CK-MB activities.
• Thin-layer isoelectric focusing was used to resolve the five serum CK-MM isoenzymes.
• The effect of EDTA (5 mmol/l) on CK-MM sub-band stability was assessed during storage at 4°C and incubation at 37°C.

Main Results:

• Total CK and CK-MB activities remained stable for two months at 4°C without EDTA.
• EDTA significantly stabilized the labile MM and MM1 sub-bands, which are early indicators of tissue damage.
• EDTA demonstrated a protective effect on the CK-MM pattern in myocardium extracts at 37°C, particularly in normal serum.

Conclusions:

• EDTA is recommended for stabilizing CK-MM sub-bands in blood samples to accurately determine the MM sub-band pattern.
• The stabilizing effect of EDTA is more pronounced at higher temperatures.
• EDTA may function by inhibiting a heat-labile component present in human serum.