Inward rectifier potassium channels in the HL‐1 cardiomyocyte‐derived cell line

HL‐1 is a line of immortalized cells of cardiomyocyte origin that are a useful complement to native cardiomyocytes in studies of cardiac gene regulation. Several types of ion channel have been identified in these cells, but not the physiologically important inward rectifier K + channels. Our aim was to identify and characterize inward rectifier K + channels in HL‐1 cells. External Ba 2+ (100 µM) inhibited 44 ± 0.05% (mean ± s.e.m., n = 11) of inward current in whole‐cell patch‐clamp recordings. The reversal potential of the Ba 2+ ‐sensitive current shifted with external [K + ] as expected for K + ‐selective channels. The slope conductance of the inward Ba 2+ ‐sensitive current increased with external [K + ]. The apparent Kd for Ba 2+ was voltage dependent, ranging from 15 µM at −150 mV to 148 µM at −75 mV in 120 mM external K + . This current was insensitive to 10 µM glybenclamide. A component of whole‐cell current was sensitive to 150 µM 4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonic acid (DIDS), although it did not correspond to the Ba 2+ ‐sensitive component. The effect of external 1 mM Cs + was similar to that of Ba 2+ . Polymerase chain reaction using HL‐1 cDNA as template and primers specific for the cardiac inward rectifier K ir 2.1 produced a fragment of the expected size that was confirmed to be K ir 2.1 by DNA sequencing. In conclusion, HL‐1 cells express a current that is characteristic of cardiac inward rectifier K + channels, and express K ir 2.1 mRNA. This cell line may have use as a system for studying inward rectifier gene regulation in a cardiomyocyte phenotype. J. Cell. Physiol. 225: 751–756, 2010. © 2010 Wiley‐Liss, Inc.