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首页> 外文期刊>American Journal of Physiology >Na+/Ca2+ exchange activity in neonatal rabbit ventricular myocytes.
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Na+/Ca2+ exchange activity in neonatal rabbit ventricular myocytes.

机译：新生兔心室肌细胞中Na + / Ca2 +交换活性。

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Much less is known about the contributions of the Na(+)/Ca(2+) exchanger (NCX) and sarcoplasmic reticulum (SR) Ca(2+) pump to cell relaxation in neonatal compared with adult mammalian ventricular myocytes. Based on both biochemical and molecular studies, there is evidence of a much higher density of NCX at birth that subsequently decreases during the next 2 wk of development. It has been hypothesized, therefore, that NCX plays a relatively more important role for cytosolic Ca(2+) decline in neonates as well as, perhaps, a role in excitation-contraction coupling in reverse mode. We isolated neonatal ventricular myocytes from rabbits in four different age groups: 3, 6, 10, and 20 days of age. Using an amphotericin-perforated patch-clamp technique in fluo-3-loaded myocytes, we measured the caffeine-induced inward NCX current (I(NCX)) and the Ca(2+) transient. We found that the integral of I(NCX), an indicator of SR Ca(2+) content, was greatest in myocytes from younger age groups when normalized by cell surface area and that it decreased with age. The velocity of Ca(2+) extrusion by NCX (V(NCX)) was linear with [Ca(2+)] and did not indicate saturation kinetics until [Ca(2+)] reached 1-3 microM for each age group. There was a significantly greater time delay between the peaks of I(NCX) and the Ca(2+) transient in myocytes from the youngest age groups. This observation could be related to structural differences in the subsarcolemmal microdomains as a function of age.
机译：与成年哺乳动物的心室肌细胞相比，关于Na（+）/ Ca（2+）交换子（NCX）和肌质网（SR）Ca（2+）泵对新生儿细胞松弛的贡献知之甚少。根据生化和分子研究，有证据表明出生时NCX的密度更高，随后在接下来的2周发育过程中会降低。因此，已经有人假设，NCX在新生儿胞质Ca（2+）下降中起相对更重要的作用，并且可能在反向模式下的兴奋收缩耦合中起作用。我们从四个不同年龄组的兔子中分离出了新生儿心室肌细胞：3、6、10和20天。使用两性霉素穿孔的膜片钳技术在氟3加载的心肌细胞中，我们测量了咖啡因诱导的内向NCX电流（I（NCX））和Ca（2+）瞬变。我们发现，I（NCX）的积分是SR Ca（2+）含量的指标，当按细胞表面积归一化时，在较年轻年龄组的肌细胞中最大，并且随着年龄的增长而降低。由NCX（V（NCX））挤出Ca（2+）的速度与[Ca（2+）]呈线性关系，并且直到每个年龄组的[Ca（2+）]达到1-3 microM时才表明饱和动力学。在最年轻的年龄组中，I（NCX）和Ca（2+）瞬变之间存在明显更大的时间延迟。该观察结果可能与肌膜下微区的结构差异随年龄变化有关。

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