Transient outward current in young and adult diseased human atria.
In human atrial fibers, the action potential undergoes a major developmental change in shape in the months immediately after birth. Transient potassium outward currents, which may affect the shape of the action potential, have been studied using a whole cell voltage-clamp technique with single cells from the atria of young patients aged 3-60 mo. Transient outward current (I(to)) amplitude was measured as the difference between the peak current and the steady-state outward current (I(late)) at the end of the voltage step. The density of I(to) was significantly reduced in adult diseased cells (n = 18) compared with normal cells (n = 21) in a large range of potential and absent in young diseased cells (n = 13). Furthermore, the I(late) recorded in young cells was significantly greater (23.7 +/- 5.74 pA/pF at 60 mV) than in adult normal cells (12.71 +/- 2.25 pA/pF at 60 mV), whereas I(late) was not significantly different between both groups of adult cells. Nevertheless, a 4-aminopyridine-sensitive I(to) has been recorded in young cells. A decrease in the frequency of clamp steps (from 0.1 to 0.01 Hz) did not reactivate a I(to) in young cells. This absence of 4-aminopyridine-sensitive Ito in young cells probably results from either a normal developmental change of this current or from pathological alterations like those described in adult diseased atria.
Mansourati
J
J
Laboratoire de Physiologie Cellulaire, Centre National de Recherche Scientifique, Orsay, France.
Le Grand
B
B
D015761:4-Aminopyridine / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D016275:Atrial Function; D002648:Child; D002675:Child, Preschool; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000187:drug effects; D006331:Heart Diseases / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000166:cytology / Q000473:pathology; D012016:Reference Values
D015761:4-Aminopyridine