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. action potential; ion channel; muscarinic receptor Address for reprint requests and other correspondence: Y.-F. Xiao, Cardiac Rhythm Disease Management, Medtronic Inc., 7000 Central Ave. NE, B252, Minneapolis, MN 55432-3576 (e-mail: yong-fu.xiao@medtronic.com )
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Electrophysiological characterization of murine HL-5 atrial cardiomyocytes
Xiao, Yong-Fu; TenBroek, Erica M.; Wilhelm, Joshua J.; Iaizzo, Paul A.; Sigg, Daniel C.
Follow AJP - Cell Physiology
, Volume 291 (3): C407
The American Physiological Society – Sep 1, 2006
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