| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1986: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1985: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1984: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
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
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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
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