单价阳离子对蛙坐骨神经中45Ca通量的影响。

The effect of monovalent cations upon 45Ca fluxes in frog sciatic nerve.

作者信息

Stout M A, Diecke F P

出版信息

Can J Physiol Pharmacol. 1980 Nov;58(11):1366-72. doi: 10.1139/y80-206.

Abstract

Investigation of Ca fluxes in desheathed bundles of myelinated nerve of frog indicates an intracellular Ca concentration of 5 x 10(-4) mol . kg-1 (axoplasm) and an average transmembrane flux of 6 x 10(-8) mol. kg-1 . s-1 at an extracellular Ca concentration of 1 mM. Replacement of extracellular Na by isosmotic sucrose increases Ca influx threefold and decreases efflux by 50%. Similar, but significantly smaller, effects are observed when Tris or choline are substituted for Na. Li replaces Na without significant changes in Ca fluxes. The data demonstrate that Ca transmembrane fluxes in this preparation are sensitive to changes in the Na gradient. The observed flux changes, however, are too small to establish a Na-Ca exchange as the sole homeostatic mechanism for intracellular Ca. Moreover, as Li appears to serve as a good Na substitute and even Tris and choline interact with Ca flux, the exchange does not show the specificity described for squid axon.

摘要

对青蛙有髓神经去鞘束中钙通量的研究表明，细胞内钙浓度为5×10⁻⁴摩尔·千克⁻¹（轴浆），在细胞外钙浓度为1毫摩尔时，平均跨膜通量为6×10⁻⁸摩尔·千克⁻¹·秒⁻¹。用等渗蔗糖替代细胞外钠会使钙内流增加三倍，并使外流减少50%。当用Tris或胆碱替代钠时，会观察到类似但明显较小的影响。锂替代钠时钙通量没有显著变化。数据表明，该制剂中的钙跨膜通量对钠梯度的变化敏感。然而，观察到的通量变化太小，无法将钠钙交换确立为细胞内钙的唯一稳态机制。此外，由于锂似乎是一种良好的钠替代物，甚至Tris和胆碱也与钙通量相互作用，这种交换并未表现出鱿鱼轴突所描述的特异性。