NA+/CA2+ EXCHANGE CURRENT-DENSITY IN CARDIAC MYOCYTES FROM RABBITS AND GUINEA-PIGS DURING POSTNATAL-DEVELOPMENT
NA+/CA2+ EXCHANGE CURRENT-DENSITY IN CARDIAC MYOCYTES FROM RABBITS AND GUINEA-PIGS DURING POSTNATAL-DEVELOPMENT
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DOI：
10.1152/ajpheart.1995.268.4.h1714
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发表时间：
1995-04-01
影响因子：
4.8
通讯作者：
COETZEE, WA
中科院分区：
文献类型：
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作者：
ARTMAN, M;ICHIKAWA, H;COETZEE, WA
有人提出，在肌浆网（SR）达到功能成熟之前，发育中的动物心脏肌膜钠/钙交换体的活性可能最强。在出生时肌浆网稀少的兔子以及肌浆网更发达的新生豚鼠身上进行了实验。采用全细胞电压钳技术对新鲜分离的单个心肌细胞中对镍离子敏感的钠/钙交换电流进行了表征。在存在钡离子、铯离子、四乙铵、D - 600和哇巴因以阻断钙离子、钠离子和钾离子电流的情况下，通过缓慢斜坡电压程序（-120到 +60 mV，0.09 V/秒）从 -40 mV的保持电位测量钠/钙交换电流。对发育中的兔子（1 - 22日龄）进行的实验表明，钠/钙交换电流密度在1 - 4日龄时最大，并在出生后的前3周迅速下降。相比之下，新生豚鼠心肌细胞中的钠/钙交换电流密度与成年豚鼠并无差异。这些结果证实，兔子和豚鼠在出生时钠/钙交换均具有功能。钠/钙交换个体发育过程中与物种相关的差异与以下概念相符：在肌浆网稀少的新生动物中，钠/钙交换起着相对更重要的作用。
It has been proposed that the activity of the cardiac sarcolemmal Na+/Ca2+ exchanger may be greatest in developing animals before the sarcoplasmic reticulum (SR) reaches functional maturity. Experiments were performed in rabbits, which have a sparse SR at birth, and in newborn guinea pigs, which exhibit a more extensive SR. Whole cell voltage clamp techniques were used to characterize the Ni2+-sensitive Na+/Ca2+ exchange current in single freshly isolated cardiac myocytes. Na+/Ca2+ exchange current was measured from a holding potential of -40 mV by using a slow-ramp voltage protocol (-120 to +60 mV, 0.09 Vis) in the presence of Ba2+, Cs+, tetraethylammonia, D-600, and ouabain to block Ca2+, Na+, and K+ currents. Experiments in developing rabbits (1-22 days old) demonstrated that Na+/Ca2+ exchange current density was greatest at 1-4 days and declined rapidly over the first 3 wk of age. In contrast, Na+/Ca2+ exchange current density in newborn guinea pig myocytes did not differ from that recorded in adults. These results confirm that Na+/Ca2+ exchange is functional at birth in both rabbits and guinea pigs. The species-related difference in the ontogeny of Na+/Ca2+ exchange is consistent with the concept that Na+/Ca2+ exchange assumes a relatively greater role in newborn animals with a sparse SR.