Wakabayashi S, Goshima K
Biochim Biophys Acta. 1981 Jul 20;645(2):311-7. doi: 10.1016/0005-2736(81)90202-9.
The kinetic characteristics of Na+-Ca2+ exchange in isolated sarcolemma vesicles from new-borne chick heart, which contain about 70% of right-side-out vesicles, were compared with those of cultured embryonic chick heart cells. Na+-Ca2+ exchange was monitored as Nai-dependent Ca2+ uptake. Increase in the internal concentration of Na+ ([Na+]i) in these two preparations caused increase in both the initial rate and the saturation-level of Ca2+ uptake. Plots of the rate of Ca2+ uptake against [Na+]i showed similar saturation-kinetics in these two preparations. The apparent Michaelis constant (Km) (0.35 mM) for Ca2+ uptake by the intact cells was much higher than that (0.031 mM) for Ca2+ uptake by the vesicles. The degree of inhibition by Mg2+ was also higher in the cells than in the vesicles. Some possible reasons (age of the chicks used, membrane potential, etc.), for these differences were examined and are discussed.
对新生鸡心脏分离肌膜囊泡（其中约70%为外翻囊泡）中Na⁺-Ca²⁺交换的动力学特征，与培养的鸡胚心脏细胞的该特征进行了比较。Na⁺-Ca²⁺交换通过监测依赖于细胞内Na⁺浓度（[Na⁺]i）的Ca²⁺摄取来进行。这两种制剂中细胞内Na⁺浓度（[Na⁺]i）的增加，导致Ca²⁺摄取的初始速率和饱和水平均增加。Ca²⁺摄取速率相对于[Na⁺]i的曲线在这两种制剂中显示出相似的饱和动力学。完整细胞摄取Ca²⁺的表观米氏常数（Km）（0.35 mM）远高于囊泡摄取Ca²⁺的表观米氏常数（0.031 mM）。Mg²⁺对细胞的抑制程度也高于对囊泡的抑制程度。对这些差异的一些可能原因（所用雏鸡的年龄、膜电位等）进行了研究并进行了讨论。
