Objective:To study the effect of Chinese herbal medicine Kangxin Fumai Granule(康心复脉颗粒 Granule for heart diseases) serum on the primary cultured sinoatrial node(SAN) cell apoptosis induced by simulated ischemia-reperfusion(IR).Methods:The SAN cells removed from SAN tissue of neonatal Wistar rats were cultured and purified with differential attachment and 5’-bromodeoxyuridine(BrdU) treatment.Simulated IR model was adopted.The obtained cells were morphologically observed with inverted microscopy.By using the method of serum pharmacology,the cell apoptosis was measured with TUNEL staining qualitatively and with flow cytometry quantitatively.Results:Three kinds of cells were observed in the cultured SAN cells:spindle,triangle and irregular.The spindle cells comprised the greatest proportion.The SAN cells in the model group showed moderate positive brown staining in the nucleus,and the apoptosis rate increased significantly compared to that in the control group(P<0.01).While the SAN cells in the Kangxin Fumai Granule high-dose group did not demonstrated positive staining in the nucleus,and the apoptosis rate decreased significantly compared to that in the model group(P<0.05).Conclusion:Of the cells cultured from SAN,the spindle cells were pacemaker cells of SAN in rats.Blockade and/or inhibition of the SAN cell apoptosis might be one of the important mechanisms of Kangxin Fumai Granule in preventing and treating sinoatrial injury induced by simulated IR. Objective: To study the effect of Chinese herbal medicine Kangxin Fumai Granule serum on the primary cultured sinoatrial node (SAN) cell apoptosis induced by simulated ischemia-reperfusion (IR). Methods: The SAN cells removed from SAN tissue of neonatal Wistar rats were cultured and purified with differential attachment and 5’-bromodeoxyuridine (BrdU) treatment. Simulated IR model was adopted. The obtained cells were morphologically observed with inverted microscopy. By using the method of serum pharmacology, the cell apoptosis was measured with TUNEL staining qualitatively and with flow cytometry quantitatively. Results: Three kinds of cells were observed in the cultured SAN cells: spindle, triangle and irregular. spindle cells comprised the greatest ratio. SAN cells in the model group exhibited -69 positive brown staining in the nucleus, and the apoptosis rate increased significantly compared to that in the control group (P <0.01) .While the SAN cells in the Kangxin Fumai Granule high-dose group did not demonstrated positive staining in the nucleus, and the apoptosis rate decreased significantly compared to that in the model group (P <0.05) .Conclusion: Of the cells cultured from SAN, the spindle cells were pacemaker cells of SAN in rats. Blockade and / or inhibition of the SAN cell apoptosis might be one of the important mechanisms of Kangxin Fumai Granule in preventing and treating sinoatrial injury induced by simulated IR.