Objectives In order to investigate the potential mechanism of Piperine, which is the active substance from Rhodobryum roseum Limpr., on acute atrial electrical remodelling in atrial fibrillation by inducing of rapid atrial pacing, as well as its protective effect on injury of oxidative stress in myocardium.

Methods 24 healthy rabbits were collected, and randomly assigned to four groups as follows: normal saline (NS), normal saline+rapid atrial pacing (NS+RAP), piperine (PI), piperine+ rapid atrial pacing (PI+RAP). In the study, acute electrical remodelling was conducted by rapid atrial pacing. In pacing group, right atrium was paced with a frequency of 500–600 bpm for 3 h, atrial effective refractory period was measured at 0 h, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h and 3 h after pacing, respectively. Then we calculated the rate adaptation of atrial effective refractory periods in different basic pacing cycle lengths. Soon after the experiment, we dissected the atrium of rabbits, the left atrium, right atrium and pulmonary veins were dissected, consequently the levels of MDA, SOD, XOD and Calcium were measured with special kits. All the results were analysed with SPSS17.0.

Results 1. In the experiment, paroxysmal atrial fibrillation or atrial tachycardia can be induced only in NS+RAP group, whereas no similar phenomenon was observed in the other three groups. 2. AERP was markedly shorter in NS+RAP group but it was not changed in NS and PI+RAP group. The rate adaptation of AERP was reduced in NS+RAP, but got lowest point (−0.24±0.59) 1 h after pacing, while the rate adaptation of AERP presented no significant changes in NS and PI group. 3. MDA of PI+RAP group in left atrium and pulmonary vein was lower than that of NS+RAP group (p<0.01), but no significant difference of MDA in RA was observed between the two groups. 4. SOD activity in PV is higher in PI+RAP than that in NS+RAP, but no significant difference was observed in other locations between PI+RAP group and NS+RAP group. 5. XOD activity in LA and PV is lower in PI+RAP than that in NS+RAP (p<0.05), but XOD activity in RA presented no difference between the two groups. 6. Calcium level in LA, RA and PV, presented lower in PI+RAP compared with that in NS+RAP group.

Conclusion 1. Piperine can help reduce incidence of AF, prevent the shortening of AERP and the rate adaptation of AERP, in other words, piperine can alleviate acute electrical remodelling in acute phase of AF. 2. Piperine can alleviate injury of oxidative stress in AF through suppression of MDA overproduction, reducing the consumption of SOD, suppression of XOD activity as well as Calcium overload, consequently develops the protective effect on myocardium during AF. 3. When AF is present, PV has the most serious injury of oxidative stress but RA suffer the slightest injury. Meanwhile, antioxidant effect of piperine is the most conspicuous in PV.