Statistical analysis
Data are presented as the mean ± standard error of the mean (SEM). Significant differences in the abundance of proteins in different tissues were identified using one-way ANOVA. Significant differences were determined when P <0.05. The intensity of Nav1.5 staining was analyzed in different areas of the AV junction, including RN, CN, INE, atrial and ventricular tissues, using quantitative immunofluorescence staining analysis. The background level of staining in each tissue section can affect the results obtained from immunofluorescence staining; thus, the staining intensity of Nav1.5 in ventricular tissue was included and used as a reference in each section used for analysis.