Creatine transporter activity and content in the rat heart supplemented by and depleted of creatine
Creatine transporter activity and content in the rat heart supplemented by and depleted of creatine
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DOI：
10.1152/ajpendo.00259.2002
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发表时间：
2003-02-01
影响因子：
5.1
通讯作者：
Neubauer, S
中科院分区：
文献类型：
--
作者：
Boehm, E;Chan, S;Neubauer, S
细胞内肌酸浓度是心肌中重要的生物能参数。尽管已知肌酸的摄取是通过 NaCl 依赖性肌酸转运蛋白 (CrT) 进行的，但对其定位和调节却知之甚少。我们研究了离体灌注心脏的 CrT 动力学，并通过使用心肌细胞测量了质膜或总裂解物中的 CrT 含量。给大鼠喂食对照饮食或补充有肌酸或肌酸类似物β-胍基丙酸（β-GPA）的饮食。对照心脏中的肌酸转运遵循饱和动力学，K-m 为 70 +/- 13 mM，V-max 为 3.7 +/- 0.07 nmol.min(-1).g 湿重 (-1)。肌酸补充显着降低了 CrT 的 V-max（2.7 +/- 0.17 nmol.min(-1).g 湿重（-1））。与此相匹配的是质膜 CrT 下降了 35%； CrT 总量没有变化。喂食 β-GPA 的大鼠表现出组织肌酸减少 80% 以上，而 β-GPA（总计）增加。 CrT 的 V-max 增加（6.0 +/- 0.25 nmol.min(-1).g 湿重（-1）），K-m 减少（39.8 +/- 3.0 mM）。质膜 CrT 增加约五倍，而总 CrT 池保持不变。我们得出的结论是，在心脏中，肌酸转运是由 CrT 质膜亚型的含量决定的，而不是由总细胞 CrT 库决定的。
The intracellular creatine concentration is an important bioenergetic parameter in cardiac muscle. Although creatine uptake is known to be via a NaCl-dependent creatine transporter (CrT), its localization and regulation are poorly understood. We investigated CrT kinetics in isolated perfused hearts and, by using cardiomyocytes, measured CrT content at the plasma membrane or in total lysates. Rats were fed control diet or diet supplemented with creatine or the creatine analog beta-guanidinopropionic acid (beta-GPA). Creatine transport in control hearts followed saturation kinetics with a K-m of 70 +/- 13 mM and a V-max of 3.7 +/- 0.07 nmol.min(-1).g wet wt(-1). Creatine supplementation significantly decreased the V-max of the CrT (2.7 +/- 0.17 nmol.min(-1).g wet wt(-1)). This was matched by an similar to35% decrease in the plasma membrane CrT; the total CrT pool was unchanged. Rats fed beta-GPA exhibited a >80% decrease in tissue creatine and increase in beta-GPA(total). The V-max of the CrT was increased (6.0 +/- 0.25 nmol.min(-1).g wet wt(-1)) and the K-m decreased (39.8 +/- 3.0 mM). The plasma membrane CrT increased about fivefold, whereas the total CrT pool remained unchanged. We conclude that, in heart, creatine transport is determined by the content of a plasma membrane isoform of the CrT but not by the total cellular CrT pool.