Differential distribution of inward rectifier potassium channel transcripts in human atrium versus ventricle.
BACKGROUND
The inward rectifier K+ current (IK1) plays an important role in governing cardiac electrical activity and is well known to have different properties in the atrium compared with the ventricle. Several inward rectifier K+ channel (IRK) subunits (hIRK, HH-IRK1, HIR, and TWIK-1) with different properties have been cloned from human tissues, but their relative expression in cardiac tissues has not been quantified. The present study was designed to define the relative levels of mRNA for various IRKs in human atrium and in failing and nonfailing ventricle.


RESULTS
Competitive reverse transcription-polymerase chain reaction was used to quantify in human atrium and ventricle the mRNA levels of hIRK, HH-IRK1, HIR, and TWIK-1. The absence of important noncardiac contamination was confirmed by demonstrating a lack of detectable mRNA markers for neuronal (acetylcholine receptor) and vascular (maxi-K channel) tissue. mRNA of HIR was more abundant in normal atrium (7.1+/-1.3 amol/ microg total RNA) than ventricle (0.6+/-0.1 amol/ microg, P<0. 05), whereas TWIK-1 mRNA was more concentrated in ventricle (18. 1+/-4.3 amol/ microg) than atrium (1.4+/-0.3 amol/ microg, P<0.05). Concentrations of hIRK (42.7+/-6.7 amol/ microg in atrium vs 57. 1+/-9.2 amol/ microg in ventricle) and HH-IRK1 (2.0+/-0.5 amol/ microg in atrium vs 1.5+/-0.5 amol/ microg in ventricle) were comparable. No significant differences in IRK subunit transcript concentrations were found between normal and failing ventricles.


CONCLUSIONS
mRNAs for all 4 IRKs are detected in human atrium and ventricle, but the mRNA copy number of a low-conductance subunit (HIR) is larger in atrium and the copy number of a weakly rectifying subunit (TWIK-1) is larger in ventricle. These differences in relative message levels may provide a potential molecular basis for different properties of IK1 in human atrium compared with ventricle.
Wang
Z
Z
Department of Medicine and Research Center, Montreal Heart Institute and University of Montreal, Montreal, Quebec, Canada. wangz@icm.umontreal.ca
Yue
L
L
White
M
M
Pelletier
G
G
Nattel
S
S
D016275:Atrial Function; D003001:Cloning, Molecular; D004553:Electric Conductivity; D005069:Evaluation Studies as Topic; D006325:Heart Atria / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D015221:Potassium Channels / Q000096:biosynthesis* / Q000235:genetics*; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger / Q000032:analysis; D013048:Specimen Handling; D014158:Transcription, Genetic / Q000235:genetics; D016276:Ventricular Function
D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger