Properties of transient outward potassium current and inward rectifier potassium current in immature human atrial myocytes.
OBJECTIVE
To study the properties of transient outward K+ current (Ito) and inward rectifier K+ current (IKl) in immature human heart.


METHODS
Ito and IKl were recorded using whole-cell patch-clamp technique in atrial myocytes isolated from 12 immature (aged from 6 months to 5 a) human hearts.


RESULTS
Ito was voltage-dependent, activated and inactivated rapidly. The IC50 (95% confidence limits) of 4-AP on Ito was 0.64 (0.48-0.87) mmol.L-1. 4-AP 1 mmol.L-1 shifted V1/2 of activation from (6.6 +/- 2.0) mV to (19.8 +/- 3.0) mV (n = 4-10, P < 0.01). 4-AP 0.3 mmol.L-1 changed V1/2 of inactivation from (-49 +/- 4) mV to (-61.4 +/- 2.1) mV (n = 3, P < 0.01), but there were no obvious influence on voltage-dependent activation of Ito (P > 0.05). At the same concentration, the recovery time constant (tau value) was prolonged from (108 +/- 16) ms to (220 +/- 67) ms (n = 3-12, P < 0.01). IKl was also voltage-dependent. Its reverse potential was -40 mV.


CONCLUSIONS
Both Ito and IKl are important K+ channel currents in immature human atrial myocytes. 4-AP can affect the inactivation and recovery of Ito at low concentration (0.3 mmol.L-1) and affect its activation at high concentration (1 mmol.L-1).
Department of Pharmacology, Institute of Materia Medica, Beijing 100050, China.
Y
Y
Liang
X M
XM
Sun
X L
XL
Wang
D015761:4-Aminopyridine / Q000494:pharmacology*; D002469:Cell Separation; D002675:Child, Preschool; D005260:Female; D006325:Heart Atria; D006801:Humans; D007223:Infant; D008297:Male; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects*
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D015761:4-Aminopyridine