ISSN:
1435-1803
Schlagwort(e):
Key words Rat – ventricular myocyte – action potential duration – transient outward current – 4-aminopyridine
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Abstract Rate-dependent alterations of action potential duration (APD) in rat ventricular myocytes were investigated. Action potentials of the isolated myocytes were recorded with patch electrodes containing EGTA (11 mM), and showed a marked rate-dependent prolongation in the APD (0.2 – 5 Hz). This prolongation was significantly inhibited in the presence of 4-aminopyridine (4-AP), a blocker of the transient outward K+ current (Ito). Thus, the rate-dependent decrease in Ito may underlie the change in APD. In contrast, the action potentials recorded from rat ventricular papillary muscles with conventional microelectrodes did not show rate-dependent alterations in the APD, i.e., the APD remained practically unaltered at the frequency range of 0.,2 – 5 Hz. These results suggest that the rate-dependent prolongation of APD (due to rate-dependent blockade of Ito) becomes evident when the intracellular Ca2+ was chelated by the internal application of EGTA via patch pipette. We speculate that the rate-dependent prolongation of APD (via decreases in Ito) is masked in the ventricular papillary muscles, probably due to rate-dependent decreases in the inward current (e.g., elcetrogenic Na+-Ca2+ exchange current) that is regulated by the intracellular calcium.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/s003950050030
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