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Updated: Apr 4, 2026
Methods for the Isolation, Culture, and Functional Characterization of Sinoatrial Node Myocytes from Adult Mice
Published on: October 23, 2016
Age-associated expression of HCN channel isoforms in rat sinoatrial node
Xin Huang1, Pei Yang2, Zhao Yang3
1Department of Cardiology, First Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Ion Channel Disease Laboratory, Key Laboratory of Environment and Genes related to Diseases of Education Ministry, Xi'an, Shaanxi 710061, P.R. China.
Insights
Aging reduces hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel proteins HCN2 and HCN4 in rat sinoatrial nodes. This decline correlates with diminished pacemaking function and reduced response to ivabradine during senescence.
Area of Science:
- Cardiovascular Physiology
- Ion Channel Biology
- Aging Research
Background:
- Hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels are crucial for cardiac pacemaking.
- Expression of HCN channel isoforms (HCN1-HCN4) varies across tissues and conditions.
- Age-related changes in HCN channel expression and function in the sinoatrial node are not well understood.
Purpose of the Study:
- To investigate the protein expression levels of HCN channel isoforms (HCN1-HCN4) in rat sinoatrial nodes (SANs) at different ages.
- To determine the functional consequences of age-associated changes in HCN channel expression on cardiac pacemaking.
- To correlate HCN channel protein levels with the effects of ivabradine, an HCN channel blocker.
Main Methods:
- Immunohistochemistry was used to detect HCN1-HCN4 protein expression in rat SANs.
- Western blot analysis was employed for quantitative assessment of HCN2 and HCN4 protein levels.
- The effect of ivabradine on heart rate was measured in intact rat hearts across different age groups.
Main Results:
- HCN2 and HCN4 proteins were confirmed in rat SANs.
- Protein levels of HCN2 and HCN4 significantly declined in aged (30-month-old) rat SANs compared to young (1-month-old) and adult (4-month-old) rats.
- The inhibitory effect of ivabradine on SAN automaticity was reduced in aged rats, correlating with lower HCN2 and HCN4 expression.
Conclusions:
- HCN2 and HCN4 protein expression in the rat sinoatrial node decreases with age.
- This age-associated decline in HCN channel expression impacts cardiac pacemaking function.
- The findings highlight the role of HCN channel alterations in the aging heart and suggest potential implications for therapeutic interventions.
Abstract:
The expression of hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel isoforms varies among species, cardiac tissues, developmental stages, and disease generation. However, alterations in the HCN channels during aging remain unclear. We investigated the protein expressions of HCN channel isoforms, HCN1-HCN4, in the sinoatrial nodes (SANs) from young (1-month-old), adult (4-month-old), and aged (30-month-old) rats. We found that HCN2 and HCN4 proteins were present in rat SAN using immunohistochemistry; therefore, we quantitatively analyzed their expression by Western blot. Aim to correlate protein expression and pacemaking function, specific blockade of HCN channels with 3 µmol/L ivabradine prolonged the cycle length in the intact rat heart. During the senescent process, the HCN2 and HCN4 protein levels declined, which was accompanied with a decreased effect of ivabradine on rat SAN automaticity. These results indicated the age-associated expression and relative function of HCN channel isoforms.
