Matlib M A, Kihara M, Farrell C, Dage R C
Department of Pharmacology and Cell biophysics, University of Cincinnati College of Medicine, OH 45267-0575.
Biochim Biophys Acta. 1988 Mar 22;939(1):173-7. doi: 10.1016/0005-2736(88)90060-0.
The existence of a Na+-Ca2+ exchange system was investigated in sarcolemmal vesicles isolated from cultured cells of dog mesenteric artery. When Na+-loaded membrane vesicles were suspended in a Na+-free KCl medium to create an outwardly directed Na+ concentration gradient across the membrane, a time-dependent uptake of Ca2+ was observed. This uptake of Ca2+ was drastically reduced when the vesicles were suspended in NaCl medium to eliminate the Na+ concentration gradient across the membrane. Monensin also decreased Ca2+ uptake in Na+-loaded vesicles. The apparent Km for Ca2+ was 2.97 microM and the apparent maximum velocity was 4.27 nmol/min per mg protein. The data indicate that a Na+-Ca2+ exchange system exists in sarcolemmal membranes isolated from cultured cells and that it is similar to the system in membranes isolated from the tissue.
在从犬肠系膜动脉培养细胞中分离出的肌膜囊泡中研究了Na⁺-Ca²⁺交换系统的存在情况。当将装载有Na⁺的膜囊泡悬浮于无Na⁺的KCl培养基中以在膜上形成外向的Na⁺浓度梯度时，观察到Ca²⁺的时间依赖性摄取。当将囊泡悬浮于NaCl培养基中以消除膜上的Na⁺浓度梯度时，这种Ca²⁺摄取大幅减少。莫能菌素也降低了装载有Na⁺的囊泡中的Ca²⁺摄取。Ca²⁺的表观Km为2.97微摩尔，表观最大速度为每毫克蛋白质4.27纳摩尔/分钟。数据表明，从培养细胞中分离出的肌膜中存在Na⁺-Ca²⁺交换系统，且它与从组织中分离出的膜中的系统相似。
