Functional expression and regulation of the hyperpolarization activated non‐selective cation current in embryonic stem cell‐derived cardiomyocytes
N Abi‐Gerges, GJ Ji, ZJ Lu… - The Journal of …, 2000 - Wiley Online Library
N Abi‐Gerges, GJ Ji, ZJ Lu, R Fischmeister, J Hescheler, BK Fleischmann
The Journal of Physiology, 2000•Wiley Online Library1 The biophysical and pharmacological characteristics of the hyperpolarization activated
non‐selective cation current (If) were recorded using whole‐cell voltage clamp in embryonic
stem (ES) cell‐derived cardiomyocytes at different stages of development. 2 The cation
current was detected in a large percentage (65%) of early stage (EDS, differentiated for 7+ 3–
4 days) cells at a current density of 11· 4±0· 6 pA pF− 1 (n= 47). In late stage (LDS,
differentiated for 7+ 9–12 days) cells the percentage of cells expressing If decreased (45%) …
non‐selective cation current (If) were recorded using whole‐cell voltage clamp in embryonic
stem (ES) cell‐derived cardiomyocytes at different stages of development. 2 The cation
current was detected in a large percentage (65%) of early stage (EDS, differentiated for 7+ 3–
4 days) cells at a current density of 11· 4±0· 6 pA pF− 1 (n= 47). In late stage (LDS,
differentiated for 7+ 9–12 days) cells the percentage of cells expressing If decreased (45%) …
- 1The biophysical and pharmacological characteristics of the hyperpolarization activated non‐ selective cation current (If) were recorded using whole‐cell voltage clamp in embryonic stem (ES) cell‐derived cardiomyocytes at different stages of development.
- 2The cation current was detected in a large percentage (65 %) of early stage (EDS, differentiated for 7 + 3–4 days) cells at a current density of 11·4 ± 0·6 pA pF−1 (n= 47). In late stage (LDS, differentiated for 7 + 9–12 days) cells the percentage of cells expressing If decreased (45 %), but If densities (15·5 ± 0·9 pA pF−1, n= 20) were increased.
- 3The muscarinic agonist carbachol (CCh, 1 μM) depressed basal If in EDS cells by 45·7 ± 6·5 %, n= 5) and was without effect in LDS cardiomyocytes (n= 4). The β‐adrenoceptor agonist isoprenaline (ISO, 1 μM) stimulated If in LDS cells by 33 ± 5·2 % (n= 6) but not in EDS cells (n= 5).
- 4Cell infusion with the catalytic subunit of the cAMP‐dependent protein kinase (PKA, 7 μM) stimulated If in EDS cells by 37·0 ± 2·9 %, (n= 4), but subsequent superfusion of 8‐bromo‐cAMP (200 μM) was without effect. Intracellular perfusion of LDS cardiomyocytes with the highly selective peptide inhibitor of PKA (PKI, 20 μM) completely inhibited the stimulation of the L‐type Ca2+ current (ICa,L) as well as of If by ISO (1 μM).
- 5Extracellular superfusion with phosphodiesterase (PDE) inhibitors – IBMX, a non‐selective antagonist, Erythro‐9‐(2‐hydoxy‐3‐nonyl)adenine (EHNA), a PDE2 antagonist and rolipram, a PDE4 antagonist – resulted in stimulation of ICa,L and If in EDS cells. By contrast, milrinone and cilostamide, two PDE3 antagonists, stimulated ICa,L, but not If.
- 6The present work demonstrates that If is functionally expressed during early cardiomyogenesis. Similar to ICa,L, If is regulated during embryonic development by phosphorylation via PKA. In contrast to ICa,L, If is not regulated by PDE3 suggesting different localization of these ion channels with respect to PDE3.
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