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001-es BibID:BIBFORM041935
Első szerző:Bányász Tamás (élettanász)
Cím:Profile of L-type Ca(2+) current and Na(+)/Ca(2+) exchange current during cardiac action potential in ventricular myocytes / Tamas Banyasz, Balazs Horvath, Zhong Jian, Leighton T. Izu, Ye Chen-Izu
Megjegyzések:OBJECTIVE: The L-type Ca(2+) current (I(Ca,L)) and the Na(+)/Ca(2+) exchange current (I(NCX)) are major inward currents that shape the cardiac action potential (AP). Previously, the profile of these currents during the AP was determined from voltage-clamp experiments that used Ca(2+) buffer. In this study, we aimed to obtain direct experimental measurement of these currents during cardiac AP with Ca(2+) cycling. METHOD: A newly developed AP-clamp sequential dissection method was used to record ionic currents in guinea pig ventricular myocytes under a triad of conditions: using the cell's own AP as the voltage command, using internal and external solutions that mimic the cell's ionic composition, and, importantly, not using any exogenous Ca(2+) buffer. RESULTS: The nifedipine-sensitive current (I(NIFE)), which is composed of I(Ca,L) and I(NCX), revealed hitherto unreported features during the AP with Ca(2+) cycling in the cell. We identified 2 peaks in the current profile followed by a long residual current extending beyond the AP, coinciding with a residual depolarization. The second peak and the residual current become apparent only when Ca(2+) is not buffered. Pharmacological dissection of I(NIFE) by using SEA0400 shows that I(Ca,L) is dominant during phases 1 and 2 whereas I(NCX) contributes significantly to the inward current during phases 3 and 4 of the AP. CONCLUSION: These data provide the first direct experimental visualization of I(Ca,L) and I(NCX) during cardiac the AP and Ca(2+) cycle. The residual current reported here can serve as a potential substrate for afterdepolarizations when increased under pathologic conditions.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Heart Rhythm. - 9 : 1 (2012), p. 134-142. -
További szerzők:Horváth Balázs (1981-) (élettanász) Jian, Zhong Izu, Leighton T. Chen-Izu, Ye
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