鸡心肌细胞膜囊泡和培养细胞中Na⁺-Ca²⁺交换动力学特征的比较。

Comparison of kinetic characteristics of Na+-Ca2+ exchange in sarcolemma vesicles and cultured cells from chick heart.

作者信息

Wakabayashi S, Goshima K

出版信息

Biochim Biophys Acta. 1981 Jul 20;645(2):311-7. doi: 10.1016/0005-2736(81)90202-9.

Abstract

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.

摘要

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。