豚鼠结肠带平滑肌中阳离子相互作用的定位

An electron microscopic method has been developed and used to study cation binding sites in smooth muscle.2. Uranyl cations normally bind to the external surface of the plasma membrane. However, uranyl also binds to the inner surface when it is accessible. Similar binding has been observed in skeletal muscle, nerve and red blood cells.3. Uranyl binds electrostatically, and the binding can be competitively reversed by other cations. By a quantitative procedure the relative affinities Ca(2+) approximately Mg(2+) >> K(+) > Na(+) for the membrane sites have been determined. This sequence is in agreement with previous values determined analytically.4. The results support a counter-cation hypothesis for the plasma membrane surfaces of the taenia coli, and may explain features of the electrical activity in smooth muscle.

已开发出一种电子显微镜方法并用于研究平滑肌中的阳离子结合位点。
铀酰阳离子通常结合于质膜的外表面。然而，当内表面可及的时候，铀酰也会与之结合。在骨骼肌、神经和红细胞中也观察到了类似的结合。
铀酰通过静电作用结合，并且这种结合可以被其他阳离子竞争性逆转。通过定量程序已确定膜位点对Ca(2+)、Mg(2+)、K(+)、Na(+)的相对亲和力为Ca(2+)≈Mg(2+)>>K(+)>Na(+)。该顺序与先前通过分析确定的值一致。
这些结果支持结肠带绦虫质膜表面的反阳离子假说，并可能解释平滑肌电活动的特征。

Localization of cation interactions in the smooth muscle of the guinea-pig taenia coli.