Distinct expression patterns of HCN channels in HL-1 cardiomyocytes.

Anne Günther,Arnd Baumann

doi:10.1186/s12860-015-0065-5

Abstract

BackgroundCardiac rhythmic activity is initiated in functionally specialized areas of the heart. Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are fundamental for these processes of cardiac physiology.ResultsHere we investigated transcript and protein expression patterns of HCN channels in HL-1 cardiomyocytes using a combination of quantitative PCR analysis and immunocytochemistry. Gene expression profiles of hcn1, hcn2 and hcn4 were acutely affected during HL-1 cell propagation. In addition, distinct expression patterns were uncovered for HCN1, HCN2 and HCN4 proteins.ConclusionsOur results suggest that HCN channel isoforms might be involved in the concerted differentiation of HL-1 cells and may indirectly affect the occurrence of contractile HL-1 cell activity. We expect that these findings will promote studies on other molecular markers that contribute to cardiac physiology.Electronic supplementary materialThe online version of this article (doi:10.1186/s12860-015-0065-5) contains supplementary material, which is available to authorized users.

Highlights

Cardiac rhythmic activity is initiated in functionally specialized areas of the heart
Antibodies Primary antibodies for immunocytochemistry were antimHCN1 (HCN1α, guinea pig, 1:500), anti-mHCN2 (HCN2α, rabbit, 1:500), and anti-mHCN4 (PG2-1A4, rat, 1:2) (Additional file 1: Table S1)
Gene expression of Hyperpolarizationactivated and cyclic nucleotide-gated (HCN) channel isoforms in HL-1 cells For investigation of HCN channel isoform gene expression, specific primers were designed to amplify defined hcn fragments. The specificity of these primers was the development of contractile HL-1 cell activity correlates with hcn gene expression, transcript levels of hcn1, hcn2 and hcn4 were quantified at different HL-1 culture densities

Summary

Introduction

Cardiac rhythmic activity is initiated in functionally specialized areas of the heart. Cardiac autonomous activity originates in the sinoatrial node (SAN) where primary pacemaker cells generate spontaneous rhythmic action potentials that trigger heart muscle contraction. Generation of rhythmic action potentials in the heart involves several channel proteins including T- and L-type Ca2+ channels, a K+ channel and a pacemaker channel [1]. Activation of T- and Ltype Ca2+ channels results in depolarization, followed by repolarization of the membrane potential due to opening of K+ channels. Near the K+ equilibrium potential pacemaker channels open and give way to an inward Na+ current. Subsequent membrane depolarization towards the threshold voltage induces a new action potential. This pacemaker current, termed Ih or If, is an essential component of cardiac automaticity [2, 3]

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