- 作者: Jian-Bing Shen Mario Vassalle
- 作者服務機構: Department of physiology and pharmacology, State University of New York, Health Science Center, Brooklyn, N.y., USA
- 中文摘要: --
- 英文摘要: The mechanisms by which different concentrations ofcesium modify membrane potentials and currents wereinvestigated in guinea pig single ventricular myocytes. Ina dose-dependent manner, cesium reversibly decreasesthe resting potential and action potential amplitude andduration, and induces a diastolic decaying voltage tail(V ), which increases at more negative and reverses atless negative potentials. In voltage-clamped myocytes,Cs+ increases the holding current, increases the outwardcurrent at plateau levels while decreasing it at potentialscloser to resting potential, induces an inward tail current(l ) on return to resting potential and causes a negativeshift of the threshold for the inward current. Duringdepolarizing ramps, Cs+ decreases the outward currentnegative to inward rectification range, whereas it in-creases the current past that range. During repolarizingramps, Cs+ shifts the threshold for removal of inward rec-tification negative slope to less negative values. Cs+-induced voltage and current tails are increased by repeti-tive activity, caffeine(5 mM) and high [Ca ]o (8.1 mM),and are reduced by low Ca (0.45 mM), Cd (0.2 mM)and Ni (2mM). Ni also abolishes the tail current thatfollows steps more positive than Eca. We conclude thatCs+(1)decreases the resting potential by decreasing theoutward current at more negative potentials, (2)shortensthe action potential by increasing the outward current atpotentials positive to the negative slope of inward rectifi-cation, and(3) induces diastolic tails through a Ca -dependent mechanism, which apparently is an en-hanced electrogenic Na-Ca exchange.
- 中文關鍵字: --
- 英文關鍵字: Myocytes, single. Cesium Voltage and current tails. Na-Ca exchange. Caicium. Cadmium. Nickel