AIM: To investigate the effects of CPU 228 on cytosolic Ca 2+ concentration ( i) and the parameters of Ca 2+ transients in myocardium during β adrenergic stimulation. METHODS: The cytosolic Ca 2+ concentration of the isolated rat ventricular myocytes was measured by Fluo 3/AM. The Ca 2+ transient of myocytes was twitched by 0.5 Hz field stimulation. Isoproterenol (ISO) 100 nmol·L -1 was used for stimulate the β adrenoceptor. The effects of CPU 228 1 μmol·L -1 on i, the intracellular Ca 2+ load level, Ca 2+ transient duration and decay ratio was observed. RESULTS: ISO 100 nmol·L -1 significantly increased the i, intracellular Ca 2+ load level, and the post peak decay ratio of cytosolic Ca 2+ , but it reduced the Ca 2+ peak duration of Ca 2+ transients in isolated rat ventricular myocytes. CPU 228 1 μmol·L -1 did not affect the i in isolated rat ventricular myocytes, but it significantly restored the ISO induced changes of i and Ca 2+ transients to control level in concentration dependent manner. CONCLUSION: CPU 228 can inhibit the increase of i, and restore the changed Ca 2+ transients to control level during β adrenergic stimulation. These effects of CPU 228 maybe due to its blockade of β adrenoceptor or relate to its signal pathway and inhibition of the hyperphosphorylation effects.