ACTION-POTENTIAL AND MEMBRANE CURRENTS OF SINGLE PACEMAKER CELLS OF THE RABBIT HEART
ACTION-POTENTIAL AND MEMBRANE CURRENTS OF SINGLE PACEMAKER CELLS OF THE RABBIT HEART
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DOI：
10.1007/bf00585507
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发表时间：
1984-01-01
影响因子：
4.5
通讯作者：
IRISAWA, H
中科院分区：
文献类型：
--
作者：
NAKAYAMA, T;KURACHI, Y;IRISAWA, H
Single, viable pacemaker cells were isolated from sinoatrial (S-A) and atrioventricular (A-V) nodes by treating with collagenase. In normal Tyrode solution containing 1.8 mM Ca2+, these pacemaker cells had a round configuration and contracted rhythmically at a frequency of .apprx. 150-260/min. The amplitude, duration and maximum rate of rise of the spontaneous action potentials recorded using patch clamp electrodes were similar to those obtained from multicellular preparations. Amplitudes of the recorded membrane current were normalized with reference to the surface area of the cell by assuming the cell shape as a plane oblate spheroid. The membrane resistance of the isolated nodal cells was 14.9 .+-. 4.0 k.OMEGA. .cntdot. cm2 (n = 12) at about -35 mV and the membrane capacitance was 1.30 .+-. 0.24 .mu.F/cm2 (n = 18). The inactivation time course of the slow inward current, isi, was fitted with a sum of 2 exponentials with time constants of 6.7 .+-. 0.6 ms and 46.6 .+-. 15.3 ms (n = 4) at +10 mV. The The amplitude of isi peaked at 0 to +10 mV in the current-voltage relationship and was 18.2 .+-. 8.4 .mu.A/cm2. The potassium current, iK, was activated in the voltage range positive to -50 mV and was saturated at about +20 mV. The amplitude of the fully activated iK at -40 mV was 3.3 .+-. 1.4 .mu.A/cm2 (n = 10) and showed an inward-going rectification. The activation of the hyperpolarization-activated current was observed at potentials negative to -70 mV in 7 of 14 experiments. The current density and membrane capacitance calculated could be overestimated and the membrane resistance underestimated, because of the presence of caveolae on the cell surface. These data give the nearest possible estimates of the electrical constants in the nodal cells, which cannot be measured accurately in the conventional multicellular preparations.
