Electrophysiological characterization of murine HL-5 atrial cardiomyocytes.
HL-5 cells are cultured murine atrial cardiomyocytes and have been used in studies to address important cellular and molecular questions. However, electrophysiological features of HL-5 cells have not been characterized. In this study, we examined such properties using whole cell patch-clamp techniques. Membrane capacitance of the HL-5 cells was from 8 to 62 pF. The resting membrane potential was -57.8 +/- 1.4 mV (n = 51). Intracellular injection of depolarizing currents evoked action potentials (APs) with variable morphologies in 71% of the patched cells. Interestingly, the incidence of successful, current-induced APs positively correlated with the hyperpolarizing degrees of resting membrane potentials (r = 0.99, P < 0.001). Only a few of the patched cells (4 of 51, 7.8%) exhibited spontaneous APs. The muscarinic agonist carbachol activated the acetylcholine-activated K(+) current and significantly shortened the duration of APs. Immunostaining confirmed the presence of the muscarinic receptor type 2 in HL-5 cells. The hyperpolarization-activated cation current (I(f)) was detected in 39% of the patched cells. The voltage to activate 50% of I(f) channels was -73.4 +/- 1.2 mV (n = 12). Voltage-gated Na(+), Ca(2+), and K(+) currents were observed in the HL-5 cells with variable incidences. Compared with the adult mouse cardiomyocytes, the HL-5 cells had prolonged APs and small outward K(+) currents. Our data indicate that HL-5 cells display significant electrophysiological heterogeneity of morphological appearance of APs and expression of functional ion channels. Compared with adult murine cardiomyocytes, HL-5 cells show an immature phenotype of cardiac AP morphology.
Cardiac Rhythm Disease Management, Medtronic Inc., 7000 Central Avenue NE, B252, Minneapolis, MN 55432-3576, USA. yong-fu.xiao@medtronic.com
Yong-Fu
YF
Xiao
Erica M
EM
TenBroek
Joshua J
JJ
Wilhelm
Paul A
PA
Iaizzo
Daniel C
DC
Sigg
D000200:Action Potentials; D000818:Animals; D002460:Cell Line; D002469:Cell Separation; D054815:Cyclic Nucleotide-Gated Cation Channels; D004594:Electrophysiology; D006325:Heart Atria / Q000166:cytology*; D006352:Heart Ventricles / Q000166:cytology; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism; D051379:Mice; D032383:Myocytes, Cardiac / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism
D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated