Journal: Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease

Article Title: Inward Rectifier K + Currents Contribute to the Proarrhythmic Electrical Phenotype of Atria Overexpressing Cyclic Adenosine Monophosphate Response Element Modulator Isoform CREM‐IbΔC‐X

doi: 10.1161/JAHA.119.016144

Figure Lengend Snippet: Experimental animals involved wild‐type mice (WT) and transgenic mice (TG) expressing the repressor isoform of cyclic adenosine monophosphate response element modulator, CREM‐IbΔC‐X, and were distributed according to age in 6‐week‐old (WT 6w and TG 6w ) and 12‐week‐old (WT 12w and TG 12w ) groups. A , Representative traces of inward rectifiers K + channel (I K1 ) recorded in WT 12w and TG 12w myocytes before and after application of 10 μmol/L BaCl 2 using a ramp protocol (inset, scale bar 0.2 seconds). The traces show current densitiy (expressed in picoamperes/picofarads [pA/pF]) over time. ( Aa ). Current–voltage plots of I K1 averaged from traces of all cells. For WT 6w , n/N are 8/5, for TG 6w n/N are 10/6, for WT 12w n/N are 13/7, and for TG 12w n/N are 9/6 ( Ab ). B , Data show mean±SE of relative mRNA levels of atrial K + voltage‐gated channel subfamily J member 2 ( Kcnj2 ) and 4 ( Kcnj4 ) normalized to WT 6w vs Hprt1 (hypoxanthine phosphoribosyltransferase 1) as the housekeeping gene; N=8 per group. Y‐axes scale is Log2. Ca through c , Representative immunoblots ( Ca ) and quantification of K + inwardly rectifying channel subunits Kir2.1 ( Cb ) and Kir2.3 ( Cc ) protein levels normalized to calsequestrin (CSQ). Data show mean±SE of 7 mice per group. Da through b , Representative action potentials recorded before (normal Tyrode [NT] as control) and after application of 10 μmol/L BaCl 2 in 1 atrial myocyte of each group ( Da ). Quantification of the percentages of action potential duration (APD) change in BaCl 2 vs NT at 50% (APD 50 ) and 90% (APD 90 ) repolarization. Data show mean±SE of n/N for WT 6w (7/5), TG 6w (5/5), WT 12w (11/6), and TG 12w (5/4) ( Db ). * P <0.05 TG 6w vs WT 6w (gray) and TG 12w vs WT 12w (black) ( A through C ) from 2‐way repeated‐measures analysis of variance with Bonferroni post hoc test ( Ab ), REST 2.07 software ( B ), and parametric or nonparametric 1‐way analysis of variance with the corresponding post hoc test ( C ); § P <0.05 BaCl 2 vs NT using Wilcoxon matched‐pairs signed‐rank test ( Db ).

Article Snippet: The following rabbit polyclonal primary antibodies were used against K + voltage‐gated channels (Kv) subunits Kv4.2 (1:200, APC 023, Alomone Labs, Jerusalem, Israel), Kv4.3 (1:200, APC 017, Alomone Labs), K + channel interacting protein 2 (KChIP2) (1:200, sc‐25685, Santa Cruz Biotechnology Inc, Santa Cruz, CA), and K + inwardly rectifying channel (Kir) subunits Kir2.1 (1:200, APC 159, Alomone Labs), Kir2.3 (1:1000, APC 032, Alomone Labs), Kir3.1 (1:200, APC 005, Alomone Labs), Kir3.4 (1:200, APC 027, Alomone Labs), and as loading control calsequestrin (1:2500, PA1‐913, Thermo Fisher Scientific).

Techniques: Transgenic Assay, Expressing, Western Blot, Software