Chin T K, Friedman W F, Klitzner T S
Department of Pediatrics, UCLA School of Medicine 90024.
Circ Res. 1990 Sep;67(3):574-9. doi: 10.1161/01.res.67.3.574.
Developmental changes in the contributions of transsarcolemmal Ca2+ influx and Ca2+ release from intracellular storage sites to myocardial contraction were evaluated in isolated ventricular myocytes from neonatal (aged 1-7 days) and adult (aged 8-10 weeks) New Zealand White rabbits. Contractions ceased in one beat when extracellular Ca2+ was decreased from 1mM to micromolar levels using a rapid perfusion technique. On reperfusion with 1 mM Ca2+, recovery of control contraction amplitude occurred after significantly fewer beats in neonatal myocytes compared with adult myocytes, and after 1 minute compared with 5 minutes of reduced Ca2+. After 15 minutes of perfusion with either 1 or 10 microM ryanodine, contraction amplitude decreased in both age groups, but the decrease was significantly greater in adults than in neonates. These experiments indicate that isolated ventricular myocytes may be used in the study of developmental changes in intracellular Ca2+ regulation. Results suggest that cardiac contraction in neonates is relatively more dependent on transsarcolemmal Ca2+ influx. Furthermore, although Ca2+ release from intracellular storage sites is present in both neonates and adults, its role in cardiac contraction is more significant in adults.
在新生（1-7日龄）和成年（8-10周龄）新西兰白兔的离体心室肌细胞中，评估了经肌膜Ca2+内流和细胞内储存部位Ca2+释放对心肌收缩贡献的发育变化。使用快速灌注技术将细胞外Ca2+从1 mM降至微摩尔水平时，收缩在一次搏动中停止。用1 mM Ca2+再灌注时，与成年心肌细胞相比，新生心肌细胞在明显更少的搏动后恢复到对照收缩幅度，与Ca2+减少5分钟相比，1分钟后恢复。在用1或10 μM 兰尼碱灌注15分钟后，两个年龄组的收缩幅度均降低，但成年人的降低幅度明显大于新生儿。这些实验表明，离体心室肌细胞可用于研究细胞内Ca2+调节的发育变化。结果表明，新生儿的心脏收缩相对更依赖于经肌膜Ca2+内流。此外，尽管新生儿和成年人都存在细胞内储存部位的Ca2+释放，但其在心脏收缩中的作用在成年人中更为显著。
