Sodium dependence of carnitine transport in isolated perfused adult rat hearts.
Sodium dependence of carnitine transport in isolated perfused adult rat hearts.
复制标题
离体灌注成年大鼠心脏中肉碱转运的钠依赖性。
DOI：
10.1152/ajpheart.1983.244.2.h247
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Neely,JR
中科院分区：
文献类型：
--
作者：
Vary,TC;Neely,JR
在心肌中，细胞内肉碱浓度比血浆肉碱浓度高约40倍，表明存在主动转运过程。在生理血清肉碱浓度（44 µM）下，心肌肉碱总摄取的 80% 通过载体介导的转运系统发生。在离体的灌注大鼠心脏中研究了这种载体介导的运输机制。肉碱转运显示出对细胞外钠浓度的绝对依赖性。在检查的每个灌注液肉碱浓度（15-100μM）下，肉碱转运速率与灌注液钠浓度线性相关。细胞外钠的完全去除完全消除了载体介导的运输。将灌流液钾浓度从对照 5.9 mM 降低至 0.6 mM，可刺激转运 35%，而将细胞外钾浓度从 5.9 mM 增加至 25 mM，可使转运减少 60%。载体介导的转运与细胞外钾浓度成反比。乙酰胆碱 (10(-3) M)、异丙肾上腺素 (10(-7) M) 或哇巴因 (10(-3)) 不会改变肉碱转运速率。添加河鲀毒素 (10(-5)) 刺激肉碱转运约 40%，而短杆菌肽 S (5 X 10(-6) M) 相对于对照，摄取量减少约 18%。数据提供了证据心肌细胞的肉毒碱转运是通过 Na+ 依赖性共转运机制发生的，该机制依赖于 Na+ 电化学梯度。
In heart muscle, the intracellular carnitine concentration is approximately 40 times higher than the plasma carnitine concentration, suggesting the existence of an active transport process. At physiological serum carnitine concentrations (44 microM), 80% of total myocardial carnitine uptake occurs via a carrier-mediated transport system. The mechanism of this carrier-mediated transport was studied in isolated perfused rat hearts. Carnitine transport showed an absolute dependence on the extracellular sodium concentration. The rate of carnitine transport was linearly related to the perfusate sodium concentration at every perfusate carnitine concentration examined (15-100 microM). Total removal of extracellular sodium completely abolished the carrier-mediated transport. Decreasing the perfusate potassium concentration from a control of 5.9 to 0.6 mM stimulated transport by 35%, whereas increasing the extracellular potassium concentration from 5.9 to 25 mM reduced transport by 60%. The carrier-mediated transport was inversely proportional to the extracellular potassium concentration. Acetylcholine (10(-3) M), isoproterenol (10(-7) M), or ouabain (10(-3) did not alter the rate of carnitine transport. Addition of tetrodotoxin (10(-5) stimulated carnitine transport by about 40%, while gramicidin S (5 X 10(-6) M) decreased uptake by about 18% relative to control. The data provide evidence that carnitine transport by cardiac cells occurs by a Na+-dependent cotransport mechanism that is dependent on the Na+ electrochemical gradient.