Distribution and role of Na+/K+ ATPase in endocardial endothelium
Distribution and role of Na+/K+ ATPase in endocardial endothelium
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DOI：
10.1016/s0008-6363(01)00412-6
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发表时间：
2001-12-01
影响因子：
10.8
通讯作者：
Sys, SU
中科院分区：
文献类型：
--
作者：
Fransen, P;Hendrickx, J;Sys, SU
目的：在哺乳动物心肌细胞中，Na+/K+ ATP酶的α亚型具有特定的定位和功能，但其在内皮细胞中的作用尚不清楚。研究方法：本文通过测定兔心乳头肌收缩参数、RT-PCR、Westernblot和免疫细胞化学等方法，对兔心内膜内皮细胞和心肌细胞中不同的α亚型进行了研究。结果：将外源性K+从5.0降至0.5mmol/l，抑制Na+/ K+ ATP酶，可引起双相性肌力作用。在外部K+为2.5 mmol/l时，+EE肌肉（内皮完整）的最大负性肌力作用显著大于-EE肌肉（内皮去除）（-22.5 +/- 2.4% vs-5.9 +/-4.0%，n=7，P 0.05）。二氢哇巴因（10（-9）~ 10（-4）mol/1，n=4）抑制Na+/K+ ATP酶，或二甲基阿米洛利（50 μ mol/1，n=6）抑制Na+-H+交换后降低K+，均仅引起非内皮依赖性正性肌力作用。RT-PCR和Western Blot显示心肌细胞中存在α（1）和α（2）Na-K-ATP酶亚型，而培养的内皮细胞中仅存在α（1）和α（2）Na-K-ATP酶亚型。免疫组织化学显示，内皮细胞中的α（1）主要存在于细胞的腔侧（n=7），α（1）和α（2）在心肌细胞中显示出不同的定位。结论：这些结果表明，+EE肌肉中Na+/K+ ATP酶抑制的负性和正性变力作用可分别归因于心内膜内皮α和肌肉α（2）亚型的抑制。因此，内皮Na+/K+ ATP酶的内皮α（1）亚型可能有助于该内皮的血-心屏障特性，并可能通过内皮Na+/H+交换控制心脏功能。(C)2001爱思唯尔科技有限公司。保留所有权利。
Objective: In mammalian cardiomyocytes, alpha isoforms of Na+/K+ ATPase have specific localisation and function, but their role in endocardial endothelium is unknown. Methods: Different a isoforms in endocardial endothelium and cardiomyocytes of rabbit Were investigated by measuring contractile parameters of papillary muscles, by RT-PCR, by Western blots and by immunocytochemistry. Results: Inhibition of Na+/ K+ ATPase by decreasing external K+ from 5.0 to 0.5 mmol/1 caused biphasic inotropic effects. The maximal negative inotropic effect at external K+ of 2.5 mmol/1 was significantly larger in +EE muscles (with intact endocardial endothelium) than in -EE muscles (with endocardial endothelium removed) (-22.5 +/- 2.4% versus -5.9 +/- 4.0%, n=7, P0.05). Inhibition of Na+/K+ ATPase either by dihydro-ouabain (10(-9) to 10(-4) mol/1, n=4) or by K+ decrease following inhibition of Na+-H+ exchanger by dimethyl-amiloride (50 mumol/1, n=6) caused endothelium-independent positive inotropic effects only. RT-PCR and Western Blot demonstrated alpha(1) and alpha(2) Na-K-ATPase isoforms in cardiomyocytes, but only a, in cultured endocardial endothelial cells. Immunohistochemistry showed that alpha(1), in endocardial endothelium was predominantly present at the luminal side of the cell (n=7) and that alpha(1) and alpha(2) displayed different localisation in cardiomyocytes. Conclusions: These results suggested that negative and positive inotropic effects of Na+/K+ ATPase inhibition in +EE muscles could be attributed to inhibition of endocardial endothelial a, and muscle alpha(2) isoform, respectively. Accordingly, the endocardial endothelial alpha(1) isoform of Na+/K+ ATPase may contribute to blood-heart barrier properties of this endothelium and may control cardiac performance via endothelial Na+/H+ exchange. (C) 2001 Elsevier Science B.V. All rights reserved.