Tetrandrine prevent connexin 40 degradation in the rabbit atria by rapid pacing

    LI Daª²Qiang, FENG Yiª²Bai, ZHANG Jaª²Ming, JIANG Junª²Ming, ZHANG Huiª²Qin, HU Huanª²Zhong

    1Department of Cardiovasology, Union Hospital, 3Department of Physiology, Tongji Medical College, Huazhong Science & Technology University, Wuhan 430022, 2Central Hospital of Engineering Bureau, CNWREP, Ankang 725011, Shaanxi, China

    ¡¾Abstract¡¿ AIM: To observe the change of connexin (Cx40) level in the rabbit atria by rapid pacing and the effect of tetrandrine on it. METHODS: Thirtyª²two rabbits were randomly divided into 3 groups: Normal control group (n=8), rapid atrial pacing group (n=12), tetrandrine group (n=12). The bipolar electrodes cather was inserted through internal jugular to the upper right atrium. Pacing were done in the latter two groups at the frequency of 600 times per minute.The infusion of tetrandrine was initiated 30 min before rapid pacing in the tetrandrine group. The other two groups were infused with the same volume of saline. the pacing duration was 16 h. The right atrial appendages were connected to perform the following examination. Na+, K+ and Ca2+ content of atrial tissues was assessed by biochemical technique. Cx40 level was examined by western blot. The electron microscopy was used to observe the ultrastructural alternation. RESULTS: Na+ and Ca2+ contents of rapid atrial pacing group were increased,but Cx40 level decreased markedly (P<0.01) comparing with the normal control group. The ultrastructure of the atrial appendages was damaged. The degradation of Cx40 and Ca2+ and Na+ overload were attenuated in tetrandrine group. CONCLUSION: Degradation of Cx40 is at least in part mediated by an increased calcium influx in the atrial cells during prolonged rapid atrial pacing. Tetrandrine can prevent Cx40 degradation and tachycardiaª² induced ultrastructural damage by inhibiting Ca2+ influx. ......