Objective. To investigate the mechanism of beating in cultured myocardiocytes through analyzing mPER1 expression and effect of melatonin on it. Method. Immunohistochemistry and melatonin interference test were employed. Result. mPER1 expression in cultured myocardiocytes showed circadian pattern, its acrophase was 15:20, its three consecutive daily average period length was approximately 23 h. melatonin had little effects on its amplitude and period, but results in its phase delayed. The observation in this study was similar to those that we previously observed in cultured murine myocardiocytes beating. Conclusion. Oscillation of mPER1 gene is one of the important reasons which cause murine myocardiocytes circadian beating. melatonin acts as "Zeitgeber" regulating mPER1 gene expression.
