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001-es BibID:	BIBFORM032954
Első szerző:	Bányász Tamás (élettanász)
Cím:	Frequency-dependent characteristics of human cardiac muscle / Tamás Bányász, János Magyar, Péter Szigligeti, Csaba Pankucsi, András Varró, Péter P. Nánási
Dátum:	1997
Megjegyzések:	OBJECTIVES: To characterize the steady state frequency-dependent properties and restitution kinetics of action potential duration (APD) in isolated human atrial and ventricular cardiac muscle preparations. MATERIALS AND METHODS: Conventional microelectrode techniques were used to record action potentials in preparations of human left ventricular muscle and right atrial appendages under steady state conditions or after abrupt changes in cycle length, ie, following increasingly longer diastolic intervals (DI). Restitution relations were generated by plotting APD against the respective DI. Restitution relations were fitted to multiexponential functions. RESULTS: Restitution of APD at 90% repolarization in ventricular preparations, paced at a basic cycle length (BCL) of 750 ms, were fitted as the sum of four exponentials, having time constants of 42.8 ms, 139 ms, 1.34 s and 16 s. Similar results were obtained for restitution of values of APD at 50% repolarization. In atrial preparations, restitution kinetics were characterized by three exponentials with time constants of 154 ms, 1.52 s and 25.5 s (BCL of 750 ms). The very fast component of restitution, observed in ventricular muscle, was apparently missing in atrial fibres. When atrial preparations were paced at a longer BCL of 5000 ms, no change in time constants of restitution was observed; however, the amplitudes of the second and third atrial components decreased significantly compared with preparations paced at a BCL of 750 ms. CONCLUSIONS: Comparing the time constant values estimated for restitution with the reported kinetic parameters of cardiac ion channels, it may be speculated that the first component of restitution in ventricular muscle is attributed to the recovery of L-type calcium current from inactivation. The lack of this very rapid component in atrial muscle can be explained by the parallel recovery of the calcium current and the transient outward potassium current, prominent in atrial myocardium. The second ventricular component (first in atrium) may be due to the time-dependent deactivation of the delayed rectifier potassium current. The third and fourth ventricular components (second and third components, respectively, in the atrium) are probably related to transient changes in intracellular ionic composition.
Tárgyszavak:	Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban egyetemen (Magyarországon) készült közlemény
Megjelenés:	Experimental And Clinical Cardiology 2 : 3 (1997), p. 205-209. -
További szerzők:	Magyar János (1961-) (élettanász) Szigligeti Péter Pankucsi Csaba (farmakológus) Varró András (1954-) (farmakológus, klinikai farmakológus) Nánási Péter Pál (1956-) (élettanász)
Internet cím:	Szerző által megadott URL Intézményi repozitóriumban (DEA) tárolt változat
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