The MAPK pathway is involved in the regulation of rapid pacing-induced ionic channel remodeling in rat atrial myocytes

Alterations to the expression L-type calcium channels (LTCCs) and Kv4.3 potassium channels form the possible basis of atrial electrical remodeling during rapid pacing. The mitogen-activated protein kinase (MAPK) pathway is affected by increases in cytoplasmic Ca2+, and therefore represents an attractive candidate for the regulation and mediation of Ca2+-induced ion channel remodeling. The present study aimed to investigate alterations to the ion channel-MAPK axis, and to determine its influence on ion channel remodeling during atrial fibrillation. Rat atrial myocytes were isolated, cultured, and in vitro rapid pacing was established. Intracellular Ca2+ signals were monitored using the Fluo-3/AM Ca2+ indicator. Verapamil, PD98058 and SB203580 were added to the culture medium of various groups at specific time-points. The mRNA expression levels of LTCC-1c and Kv4.3 potassium channels were detected by reverse transcription-polymerase chain reaction. Western blotting was performed to determine the expression levels of channel and signaling proteins. The results demonstrated that fast pacing significantly increased the intracellular Ca2+ concentration in atrial myocytes, whereas treatment with verapamil markedly inhibited this increase. In addition, verapamil significantly antagonized the rapid pacing-induced activation of extracellular signal-regulated kinase (ERK) and p38MAPK. These results indicated that the MAPK pathway may have an important role in the opening of LTCCs, and alterations to MAPK molecule expression could affect the expression and remodeling of ion channels.