Influence of rapid atrial pacing on the expression of ?1c subunit of L-type calcium channel and the protective effect of verapamil / 解放军医学杂志

ABSTRACT

Obiective To investigate the influence of rapid atrial pacing(RAP)on the expression of ?1c subunit of L-type calcium channel,and the protective effect of verapamil.Methods 30 rabbits were randomly assigned into RAP group and verapamil pre-conditioned group.Each group was further divided into 5 subgroups(n=3 for each subgroup).Electrode was embedded in the right atrium through right external jugular vein.Pacing was performed for 6h,12h,24h and 48h in different subgroups.No pacing in the sham operation group.For verapamil pre-conditioned group,the drug was intravenously administered(0.2mg/kg)30 minutes before the initiation of rapid atrial pacing.Right atrium tissue was harvested for determination of mRNA and protein expression of L-type calcium channel subunits by reverse transcription polymerase chain reaction(RT-PCR)and Western blot.Results The mRNA level of ?1c subunit started to be reduced 6h after rapid atrial pacing(RAP)and continued to decline as pacing continued,and the expression of protein was parallel with mRNA.Otherwise,the mRNA level of ?1c subunit started to decrease 24h after RAP and continued to decline while pacing continued,and the expression of protein paralleled with that of mRNA in verapamil pre-conditioned group.Verapamil can attenuate the down-regulation of L-type calcium channel of the atrium induced by RAP only at 24h after RAP,but the effect was less intent.Conclusion mRNA and protein expression level of L-type calcium channel subunits decreased after RAP,The calcium channel blocker verapamil can attenuate the down-regulation of L-type calcium channel of atrium induced by RAP resulting in a decrease or postponement of calcium overload in atrial myocytes,thus exerting protective effects on atrial electrical remodeling,but such effects vanished after prolonged pacing.