Slaughter R S, Shevell J L, Felix J P, Garcia M L, Kaczorowski G J
Department of Membrane Biochemistry and Biophysics, Merck Institute for Therapeutic Research, Rahway, New Jersey 07065.
Biochemistry. 1989 May 2;28(9):3995-4002. doi: 10.1021/bi00435a055.
Membrane vesicles which exhibit high levels of Nai-dependent Ca2+ uptake have been prepared from either porcine or bovine aortic smooth muscle. These membranes are identified as being of sarcolemmal origin by enrichment of marker activities associated with the sarcolemma (e.g., binding of the ligands PN 200-110, iodocyanopindolol, and ouabain). The Vmax of Na-Ca exchange in the two aortic sarcolemmal preparations [0.5-3.5 nmol s-1 (mg of protein)-1] is significantly higher than that previously reported with membrane preparations derived from visceral and vascular smooth muscle and compares favorably with maximal values recorded in cardiac sarcolemmal membrane vesicles [5-20 nmol-1 s-1 (mg of protein)-1] under identical experimental conditions. The Km of Ca2+ (15 +/- 5 microM) and the Km of Na+ (15 +/- 7 mM) are similar values as determined in heart. Aortic and cardiac Na-Ca exchange activities are equivalent in their sensitivity to inhibition by La3+ and two known classes of mechanism-based organic blockers of transport activity (i.e., amiloride analogues and bepridil-like agents). Both also display electrogenic behavior. However, Li+, K+, and choline all inhibit the smooth muscle transporter with markedly greater potency than found in heart, and intravesicular Ca2+ does not affect transport activity in smooth muscle membranes as it does in the cardiac system. When maximal transport velocities are compared, aortic membrane vesicles have 3-6-fold higher Na-Ca exchange than sarcolemmal Ca2+-ATPase Ca2+ transporting capacities.(ABSTRACT TRUNCATED AT 250 WORDS)
已从猪或牛的主动脉平滑肌中制备出表现出高水平钠依赖性钙摄取的膜泡。通过与肌膜相关的标记活性富集（例如，配体PN 200-110、碘氰吲哚洛尔和哇巴因的结合），这些膜被鉴定为肌膜来源。两种主动脉肌膜制剂中钠-钙交换的Vmax[0.5-3.5 nmol s-1（mg蛋白质）-1]显著高于先前报道的来自内脏和血管平滑肌的膜制剂，并且在相同实验条件下与心脏肌膜泡中记录的最大值[5-20 nmol-1 s-1（mg蛋白质）-1]相当。钙的Km（15±5 microM）和钠的Km（15±7 mM）与在心脏中测定的值相似。主动脉和心脏的钠-钙交换活性对镧离子和两种已知的基于机制的运输活性有机阻滞剂（即氨氯地平类似物和苄普地尔样药物）抑制的敏感性相当。两者也都表现出电生行为。然而，锂、钾和胆碱对平滑肌转运体的抑制效力明显高于心脏，并且囊泡内钙不像在心脏系统中那样影响平滑肌膜中的运输活性。当比较最大转运速度时，主动脉膜泡的钠-钙交换比肌膜钙ATP酶的钙转运能力高3-6倍。（摘要截断于250字）
