Document Type : Original Article
STEM CELLS DEPARTMENT, ROYAN INSTITUTE,TEHRAN, IRAN
Introduction: Lactate dehydrogenase is one of the cardiac enzyme markers, studied in vivo. In the present study, activity and kinetic properties of enzyme extracted from cardiomycytes derived from mouse embyronic stem cell in vitro were compared with enzyme extracted mouse neonatal from cardiomyocytes in vivo.
Material and Methods: Mouse embryonic stem cells were cultured and differentiated and there after cardiomyocytes were separated from mouse neonatal heart and studied by immunocytological methods. Both cells were sonicated, total protein was extracted and kinetic properties were determined by enzyme assay.
Results: Immunocytological study confirmed existence of two purified cell types. With spectrophotometic methods, enzyme activity was determined and kinetic constants for NAD+ were calculated. In the embryonic stem cell-derived cardiomyocytes specific activity value was 16.78±1.02 μmol min -1 mg-1 and Km value was 0.37±0.03mM. The neonatal cardiomyocyte specific activity value was 29.41±1.87 μmol min -1 mg-1 and Km value was 0.69±0.04 mM (r2>0.95). The optimum temperature for embyronic stem cell-derived cardiomyocyte and natural cardiomyocyte derived enzymes were 65°C, 60°C, respectively. The optimum pH for forward reaction was 8 for both enzyme preparations.
Conclusion: Differences between kinetic properties of both enzymes were observed.