Analysis of mechanisms of controlling <Ca^(2+)> -channels in myocardium transplanted into the renal capsular space of the rat

1.本文用双管离子选择性微电极测定了不同频率和周期重复刺激离体豚鼠乳头肌引起的膜电位（MP）、细胞内外钾离子和细胞内钠离子活度（<a^o_k>、<a^i_k>和a <N^i_a>）的变化。刺激（2- 4 Hz）使细胞去极化，终止刺激引起超极化。<a^i_k>和a <n^i_a>（0.1 Hz刺激）分别为92.3 <-！+> 4.6 mM和7.8 <-！+> 2.0 mM（平均值<-！+> SD）。延长刺激时间（0.5 ~ 2 min），a <N^i_a>呈时间依赖性增加，但刺激时间超过3 min，a <N^i_a>的增加不明显。刺激终止后，a <N^i_a>呈指数下降。<a^i_k>在3- 4 Hz刺激下略有下降。<a^o_k>在刺激期间增加，在刺激后下降到低于初始水平。 ...更多信息 刺激的终结。结果表明，在豚鼠乳头肌中，钠钾泵的产电成分对刺激后超极化的贡献很小，因为超极化主要是由钠钾泵活性引起的<a^o_k>耗竭.我们建立了一种新的缺血心肌电生理研究模型。将从新生大鼠心脏切除的心室组织片（1 × 1 mm）移植到纯品系F344-NSlc的成年大鼠的肾包膜空间中。7-10天后，当组织完全血管化时，用常规微电极技术原位检测移植细胞在正常循环和肾动脉结扎引起的缺血期间的电生理特性。跨膜电位在单个细胞中变化，范围为-60至-90 mV。从移植细胞记录的自发发生的动作电位的幅度，持续时间和配置是类似的新生和成年大鼠心肌。少

1. We measured changes in membrane potential (MP), extra-and intracelllar potassium and intracellular sodium ion activities ( <a^o_k> , <a^i_k> and a <N^i_a> ) in papillary muscle of the guinea-pig heart induced by repetitive stimulation at various frequencies and periods in vitro, using double barrelled ion-selective microelecrodes. Stimulation (2-4Hz) depolarized the cells, and termination of stimulation induced hyperpolarization. <a^i_k> and a <n^i_a> (stimulated at 0.1 Hz) were 92.3 <-!+> 4.6 mM, and 7.8 <-!+> 2.0mM (mean <-!+> SD), respectively. Prolongation of the stimulation period (0.5-2 min) increased a <N^i_a> timedependently, but there was no further increase by stimulation for longer than 3 min. The increase in a <N^i_a> was dependent on stimulus-frequency. Afer termination of the stimulation, a <N^i_a> declined exponentially. <a^i_k> slightly decreased by the stimulation (3-4Hz). <a^o_k> increased during the stimulation period, and decreased below the initial level after t … More ermination of the stimulation. Results suggests that in guinea-pig papillary muscle, the contribution of an electrogenic component of Na-K pump to the hyperpolarization after stimulation would be small, since the hyperpolarization could be explained mostly by depletion of <a^o_k> induced by Na-K pump activity.2. We have developed a new model for electrophysiological studies on ischemic myocardium in situ. Pieces of ventricullar tissue(lxlmm) excised from the neonatal rat heart were transplanted into the renal capsular space of the adult rat of the pure strain F344-NSlc. Electrophysiological properies of the transplanted cells during normal circulation and during ischemia induced by ligation of the renal artery were examined in situ 7-10 days later, when the tissues were fully vascularized, by means of conventional microelectrode techniques. Transmembrane potentials varied in individual cells, ranging from -60 to -90mV. The amplitude, duration, and configuration of spontaneously occuring action potentials recorded from the transplanted cells were similar to those obtained in neonatal and adult rat myocardium. Less