| Autor: |
Zobel, Carsten, Cho, Hee Cheol, Nguyen, The‐Tin, Pekhletski, Roman, Diaz, Roberto J., Wilson, Gregory J., Backx, Peter H. |
| Zdroj: |
Journal of Physiology; July 2003, Vol. 550 Issue: 2 p365-372, 8p |
| Abstrakt: |
Cardiac inward rectifier K+currents (IK1) play an important role in maintaining resting membrane potential and contribute to late phase repolarization. Members of the Kir2.xchannel family appear to encode for IK1. The purpose of this study was to determine the molecular composition of cardiac IK1in rabbit ventricle. Western blots revealed that Kir2.1and Kir2.2, but not Kir2.3, are expressed in rabbit ventricle. Culturing rabbit myocytes resulted in a ∼50 % reduction of IK1density after 48 or 72 h in culture which was associated with an 80 % reduction in Kir2.1, but no change in Kir2.2, protein expression. Dominant‐negative (DN) constructs of Kir2.1, Kir2.2and Kir2.3were generated and tested in tsA201 cells. Adenovirus‐mediated over‐expression of Kir2.1dn, Kir2.2dnor Kir2.1dnplus Kir2.2dnin cultured rabbit ventricular myocytes reduced IK1density equally by 70 % 72 h post‐infection, while AdKir2.3dnhad no effect, compared to green fluorescent protein (GFP)‐infected myocytes. Previous studies indicate that the [Ba2+] required for half‐maximum block (IC50) differs significantly between Kir2.1, Kir2.2and Kir2.3channels. The dependence of IK1on [Ba2+] revealed a single binding isotherm which did not change with time in culture. The IC50for block of IK1was also unaffected by expression of the different DN genes after 72 h in culture. Taken together, these results demonstrate functional expression of Kir2.1and Kir2.2in rabbit ventricular myocytes and suggest that macroscopic IK1is predominantly composed of Kir2.1and Kir2.2heterotetramers. |
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