Key Points
- To determine whether cell-to-cell heterogeneity in Kv2.1 mRNA expression explains the functional variation of the delayed rectifier potassium current in single rat left ventricular myocytes.
- Isolated midmyocardial myocytes from the rat left ventricular free wall positive for alpha-myosin heavy chain mRNA (n=74).
- Conducted whole-cell patch-clamp recordings to evaluate delayed rectifier current (I(K)) and tetraethylammonium-sensitive outward current (I(TEA)) at V(Pip)=40 mV.
- Performed multiplex single-cell RT-PCR on the recorded cells to correlate individual electrophysiological properties with Kv2.1 and Kv4 mRNA expression.
- Kv2.1 mRNA was detected in 47% of ventricular myocytes (n=74), while I(K) and I(TEA) magnitudes varied broadly from 200 to 1450 pA and 150 to 1130 pA, respectively.
- Combined patch-clamp and RT-PCR analysis showed no significant differences in I(K) or I(TEA) amplitude or inactivation kinetics between cells expressing Kv2.1 mRNA and those lacking it.
- Kv4 mRNA was consistently detected in all midmyocardial myocytes displaying the transient outward potassium current (I(to1), n=10).
Structured PICO
PPopulationSingle isolated midmyocardial myocytes from the rat left ventricular free wall (n=74)
IInterventionMultiplex single-cell RT-PCR and whole-cell patch-clamp recordings
CComparatorMyocytes not expressing Kv2.1 mRNA
OOutcomeMagnitude and inactivation kinetics of delayed rectifier current (I(K)) and TEA-sensitive outward current (I(TEA))surrogate
Heterogeneity of the delayed rectifier current among individual rat left ventricular myocytes cannot be explained by the distribution pattern of Kv2.1 mRNA.