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

1. 我们利用双管离子选择微电极，在体外测量了不同频率和周期重复刺激诱导豚鼠心脏乳头肌膜电位（MP）、胞外和胞内钾离子和胞内钠离子活性（<a^o_k>、<a^i_k>和<N^i_a>）的变化。刺激（2-4Hz）使细胞去极化，刺激终止诱导超极化。<a^i_k>和a <n^i_a> （0.1 Hz刺激）为92.3 <-！+> 4.6 mM，和7.8 <-！+> 2.0mM（平均<-!）+> SD)。延长刺激时间（0.5-2 min）可增加<N^i_a>时间，但刺激时间超过3 min后无进一步增加。a <N^i_a>的增加依赖于刺激频率。增产结束后，a <N^i_a>呈指数下降。<a^i_k>在3 ~ 4hz的刺激下略有下降。<a^o_k>在刺激期间升高，在刺激结束后降至初始水平以下。结果表明，在豚鼠乳头肌中，Na-K泵的电致成分对刺激后的超极化的贡献很小，因为超极化主要可以解释为Na-K泵活动引起的<a^o_k>耗竭。我们建立了一种原位缺血心肌电生理研究新模型。将从新生大鼠心脏切除的心室组织（lxlmm）块移植到F344-NSlc纯株成年大鼠肾包膜间隙中。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在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。单个细胞的跨膜电位变化范围为-60 ~ -90mV。从移植细胞中记录的自发动作电位的振幅、持续时间和结构与在新生和成年大鼠心肌中获得的相似。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