Role of the sarcoplasmic reticulum in contraction and relaxation of immature rabbit ventricular myocytes
Role of the sarcoplasmic reticulum in contraction and relaxation of immature rabbit ventricular myocytes
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DOI：
10.1006/jmcc.1997.0509
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发表时间：
1997-10-01
影响因子：
5
通讯作者：
Artman, M
中科院分区：
文献类型：
--
作者：
Balaguru, D;Haddock, PS;Artman, M
先前对新生儿心脏的间接研究表明，SR的功能作用降低，并且对反式Sarcolemmal Ca2+通量的依赖性更大，以直接引起收缩并促进放松。 We tested the hypothesis that the SR in newborn rabbit hearts is functionally incompetent by measuring contraction and relaxation in ventricular myocytes isolated from the hearts Df 1-2-day-old (newborn), 10-12-day-old (juvenile) and > 150天大的（成人）兔子。将电刺激的抽搐特性与在存在和不存在功能性肌膜Na-Ca交换的情况下快速应用10 mM咖啡因（使用Na+ - 和Ca2+无细胞外溶液禁用）的抽动特性。在稳态期间，与成年肌细胞相比，新生儿和少年的电诱导的收缩幅度较低（2.9 +/- 0.5和3.4 +/- 0.3 V 8.5 V 8.5 +/- 10.9％的静息细胞长度的10.9％； n = 24--- 29）和未成熟的肌细胞（t（0.75））值较慢：新生儿250 +/- 20；少年240 +/- 10;成人130 +/- 20 ms，n = 14-21）。与我们的假设相反，咖啡因引发了足够的SR Ca2+从未成熟的心肌释放，从而引发了与成年人相似的收缩。 （新生儿12.8 +/- 1.1;少年14.0 +/- 0.9;成人15.0 +/-静息细胞长度的1.6％，n = 25-29）。在稳态抽搐期间，Indo-1 Ca2 +瞬变的幅度为36 +/- 12％的新生儿中最大咖啡因诱导的Ca2 +瞬变（n = 6），成人中的59 +/- 4％（n = 6）。咖啡因在成年肌细胞（t（0.75）= 200 +/- 30 ms）中略长时间放松，但在新生儿和少年肌细胞中加速放松（t（0.75）= 180 +/- 20和150 +/-30 +/- 30 ms） 。当禁用SR和NA-CA交换器时，新生儿和少年肌细胞的放松速率（归因于肌膜Ca2 +-ATPase和线粒体Ca2 +Uniporter）的速度明显快于成人（1660 +/-210 +/-210 +3030 +3030 +3030 +3030 +3030 +3030 +3030 + /-180 V 4530 +/- 310 ms，n = 14-21）。我们得出的结论是，新生儿和成年兔心室肌细胞具有可比的SR Ca2+负载，但是新生儿细胞在稳态收缩期间表现出较小的分数SR Ca2+释放，而在弛豫过程中通过肌毛肌NA-CA换出更大的Ca2+去除。 （c）1997 Academic Press Limited。
Previous indirect studies of newborn hearts have suggested a diminished functional role of the SR and a greater dependency upon trans-sarcolemmal Ca2+ fluxes to directly elicit contraction and promote relaxation. We tested the hypothesis that the SR in newborn rabbit hearts is functionally incompetent by measuring contraction and relaxation in ventricular myocytes isolated from the hearts Df 1-2-day-old (newborn), 10-12-day-old (juvenile) and >150-day-old (adult) rabbits. Electrically stimulated twitch characteristics were compared to those elicited by the rapid application of 10 mM caffeine in the presence and absence of functional sarcolemmal Na-Ca exchange (disabled using a Na+- and Ca2+-free extracellular solution). During steady state, electrically-induced contractions were lower in amplitude in newborn and juvenile compared to adult myocytes (2.9 +/- 0.5 and 3.4 +/- 0.3 v 8.5 +/- 10.9% of resting cell length, respectively; n=24-29) and relaxation was slower in immature myocytes (t(0.75)) values: newborn 250 +/- 20; juvenile 240 +/- 10; adult 130 +/- 20 ms, n=14-21). Contrary to our hypothesis, caffeine triggered sufficient SR Ca2+ release from immature myocytes to elicit contractions of similar magnitude to adults; (newborn 12.8 +/- 1.1; juvenile 14.0 +/- 0.9; adult 15.0 +/- 1.6% of resting cell length, n=25-29). The amplitude of indo-1 Ca2+ transients during steady-state twitch was 36 +/- 12% of the maximal caffeine-induced Ca2+ transient in newborns (n=6) and 59 +/- 4% in adults (n=6). Caffeine slightly prolonged relaxation in adult myocytes (t(0.75)=200 +/- 30 ms), but accelerated relaxation in newborn and juvenile myocytes (t(0.75)=180 +/- 20 and 150 +/- 30 ms, respectively). When both the SR and Na-Ca exchanger were disabled, the rate of relaxation (attributable to the sarcolemmal Ca2+-ATPase and mitochondrial Ca2+ uniporter) of newborn and juvenile myocytes was significantly faster than in the adults (1660 +/- 210 and 3030 +/- 180 v 4530 +/- 310 ms, respectively; n=14-21). We conclude that neonatal and adult rabbit ventricular myocytes have comparable SR Ca2+ load, but neonatal cells exhibit smaller fractional SR Ca2+ release during steady-state contractions and greater Ca2+ removal by sarcolemmal Na-Ca exchange during relaxation. (C) 1997 Academic Press Limited.