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首页> 外文期刊>Canadian Journal of Physiology and Pharmacology >Functional differences of Na+/Ca2+ exchanger expression in Ca2+ transport system of smooth muscle of guinea pig stomach.
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Functional differences of Na+/Ca2+ exchanger expression in Ca2+ transport system of smooth muscle of guinea pig stomach.

机译：Na + / Ca2 +交换子在豚鼠胃平滑肌Ca2 +转运系统中的功能差异

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摘要

The plasma membrane ATP-dependent Ca2+ pump and the Na+/Ca2+ exchanger (NCX) are the major means of Ca2+ extrusion in smooth muscle. However, little is known regarding distribution and function of the NCX in guinea pig gastric smooth muscle. The expression pattern and distribution of NCX isoforms suggest a role as a regulator of Ca2+ transport in cells. Na+ pump inhibition and the consequent to removal of K+ caused gradual contraction in fundus. In contrast, the response was significantly less in antrum. Western blotting analysis revealed that NCX1 and NCX2 are the predominant NCX isoforms expressed in stomach, the former was expressed strongly in antrum, whereas the latter displayed greater expression in fundus. Isolated plasma membrane fractions derived from gastric fundus smooth muscle were also investigated to clarify the relationship between NCX protein expression and function. Na+-dependent Ca2+ uptake increased directly with Ca2+ concentration. Ca2+ uptake in Na+-loaded vesicles was markedly elevated in comparison with K+-loaded vesicles. Additionally, Ca2+ uptake by the Na+- or K+-loaded vesicles was substantially higher in the presence of A23187 than in its absence. The result can be explained based on the assumption that Na+ gradients facilitate downhill movement of Ca2+. Na+-dependent Ca2+ uptake was abolished by the monovalent cationic ionophore, monensin. NaCl enhanced Ca2+ efflux from vesicles, and this efflux was significantly inhibited by gramicidin. Results documented evidence that NCX2 isoform functionally contributes to Ca2+ extrusion and maintenance of contraction-relaxation cycle in gastric fundus smooth muscle.
机译：质膜ATP依赖性Ca2 +泵和Na + / Ca2 +交换剂（NCX）是平滑肌中Ca2 +挤出的主要手段。然而，关于NCX在豚鼠胃平滑肌中的分布和功能的了解还很少。 NCX亚型的表达模式和分布表明，其在细胞中作为Ca2 +转运的调节剂。 Na +泵的抑制作用以及随之而来的K +的去除导致眼底逐渐收缩。相比之下，胃窦反应明显较少。 Western印迹分析显示，NCX1和NCX2是胃中主要表达的NCX同种型，前者在胃窦中强烈表达，而后者在眼底中表达更高。还研究了分离自胃底平滑肌的质膜级分，以阐明NCX蛋白表达与功能之间的关系。 Na +依赖性的Ca 2+吸收随Ca 2+浓度的增加而直接增加。与K +载泡相比，Na +载泡中Ca 2+的摄取显着增加。另外，在有A23187的情况下，由Na +或K +负载的小泡对Ca 2+的吸收要比不存在A2187时高得多。可以基于Na +梯度有助于Ca2 +下坡运动的假设来解释结果。单价阳离子离子载体莫能菌素消除了Na +依赖性的Ca2 +吸收。 NaCl增强了小泡中Ca2 +的流出，而这种短杆菌肽显着抑制了这种流出。结果有证据表明，NCX2亚型在功能上有助于Ca2 +的挤出和维持胃底平滑肌收缩松弛周期。

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