Expression changes of ionic channels in early phase of cultured rat atrial myocytes induced by rapid pacing

BACKGROUND Recent studies have demonstrated that atrial electrical remodeling was an important contributing factor for the occurrence, persistence and maintenance of atrial fibrillation. The expression changes of ionic channels, especially L-type calcium channel and potassium channel Kv4.3, were the important molecular mechanism of atrial electrical remodeling. This study aimed to observe the expression changes of ionic channels in a rapid paced cell model with primary cultured atrial myocytes. METHODS The primary rat atrial myocytes were cultured, characteristics of the cultured myocytes were observed with light microscope and the cell phenotype was harvested by immunocytochemical stain to detect α-actin. The cellular model of rapid pacing was established with primary cultured atrial myocytes. The expressions of L-type calcium channel α1c and potassium channel Kv4.3 in cultured atrial myocytes were detected by immunocytochemistry, reverse transcription polymerase chain reaction and Western blot after rapid pacing. RESULTS The primary rat atrial myocytes were isolated and cultured successfully, and used for following experiment by identification of activity and purity. Cellular model of rapid electrical field pacing was established successfully. There is no significant difference in cell activity after pacing compared to that before pacing by 3-[4, 5-dimethylthiazol-2-y1]-2, 5-diphenytetrazolium bromide assay, and cell degeneration can be observed by transmission electron microscope. The mRNA expression of L-type calcium channel α1c started to reduce after 6 h of rapid pacing and continued to decline as pacing continued. Protein expression changes were paralleled with decreased mRNA expression of the L-type calcium channel α1c. The mRNA expressions of potassium channel Kv4.3 were not altered within the first 6 h, but after 12 h, mRNA expressions were reduced. Longer pacing periods did not further decrease mRNA expression of potassium channel Kv4.3. Protein expression changes were paralleled with decreased mRNA expression of potassium channel Kv4.3. CONCLUSIONS Rapid paced cultured atrial myocyte model was established utilized primary cultured atrial myocytes and this model can be used for studying the early electrical remodeling in atrial fibrillation. Expressions of L-type calcium channel α1c and potassium channel Kv4.3 were both reduced at different levels in early phase of rapid pacing atrial myocytes. It implicates the occurrence of ionic channel remodeling of atrial myocytes.