LEAF A, HAYS R M
J Gen Physiol. 1962 May;45(5):921-32. doi: 10.1085/jgp.45.5.921.
Measurements have been made of the permeability of the isolated urinary bladder of the toad to a number of small solute molecules, in the presence and absence of vasopressin. Vasopressin has a strikingly specific effect on increasing permeability of the bladder to a group of small, uncharged amides and alcohols while penetration by other small molecules and ions is unaffected. The movement of urea is passive, as indicated by equal flux rates in the two directions. The reflection coefficients for chloride and thiourea indicate a high degree of impermeability of the bladder to these solutes even in the presence of large net movements of water. The low concentration of thiourea in the tissue water when this compound is added to the mucosal bathing medium indicates that the major permeability barrier to thiourea is at the mucosal surface of the bladder. The findings can be accounted for by a double permeability barrier consisting of a fine selective diffusion barrier and a porous barrier in series. The former would constitute the permeability barrier to most small solutes while the latter would be the rate-limiting barrier for water and the amides. It would be the porous barrier which is affected by vasopressin. Reasons are presented which require both barriers to be contained in or near the plasma membrane at the mucosal surface of the bladder.
在有和没有抗利尿激素的情况下，对蟾蜍离体膀胱对多种小分子溶质的渗透性进行了测量。抗利尿激素对增加膀胱对一组小的、不带电荷的酰胺和醇的渗透性具有显著的特异性作用，而其他小分子和离子的渗透则不受影响。尿素的移动是被动的，这由两个方向上相等的通量率表明。氯化物和硫脲的反射系数表明，即使在存在大量水的净移动时，膀胱对这些溶质也具有高度的不渗透性。当将硫脲添加到粘膜浴液介质中时，组织水中硫脲的浓度较低，这表明硫脲的主要渗透屏障位于膀胱的粘膜表面。这些发现可以用由精细的选择性扩散屏障和串联的多孔屏障组成的双重渗透屏障来解释。前者将构成对大多数小分子溶质的渗透屏障，而后者将是水和酰胺的限速屏障。受抗利尿激素影响的将是多孔屏障。文中给出了一些理由，这些理由要求两个屏障都包含在膀胱粘膜表面的质膜内或附近。
