Atrial funny current (If) density and hyperpolarization-activated cyclic nucleotide-gated channel expression in atrial fibrillation patients with rheumatic heart disease

Abstract

Objective To study the changes of both funny current (If) density and expression levels of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel in muscles of right atrium in rheumatic heart disease patients with atrial fibrillation (AF) in comparison to those in normal sinus rhythm (SR).Methods Ifdensity was measured by using whole-cell patch clamp technique in single myocyte isolated by an enzymatic dissociation method from right atrial appendages in patients with AF (n =25) and those with SR (n =16).The expression levels of HCN channe1 were also determined in right atrial appendages from patients with AF and those with SR by Western boltting.Results Ifdensity in single myocyte was significantly increased at same test potential in AF compared to that in SR.And the difference reached peak with the test potential of-70 mV [(-43.74 ±2.87) vs.(-26.81 ± 1.41) pA/pF,P ＜0.01].The expression levels of HCN2 and HCN4 channels were also significantly higher in AF than those of SR [(0.44 ±0.20) vs.(0.23 ±0.13) and (0.53 ±0.20) vs.(0.36 ±0.18),P ＜0.01].Conclusion The data suggest that the increase of If density and HCN channel up-regulation might contribute to the atrial electrical remodeling which participates in the progress of AF development in rheumatic heart disease. Key words: Atrial fibrillation; Hyperpolarization-activated cyclic nucleotide-gated channel expression; Patch-clamp techniques