Kachadorian W A, Levine S D
J Membr Biol. 1982;64(3):181-6. doi: 10.1007/BF01870884.
We recently described a method by which the resistance to water flow of the luminal membrane of ADH-stimulated toad bladder can be quantitatively distinguished from that of barriers lying in series with it. This method requires estimated of both total bladder water permeability (assessed by transbladder osmotic water flow at constant gradient) and luminal membrane water permeability (assessed by quantitation of the frequency of ADH-induced luminal membrane particle aggregates). In the present study we examined the effect of bladder distension on transepithelial osmotic water flow before and during maximal ADH stimulation. Base-line water flow was unaffected by bladder distension, but hormonally stimulated flow increased systematically as bladders became more distended. Distension had no effect on the frequency of ADH-induced intramembranous particle aggregates. By comparing the relationships between aggregate frequency and hormonally induced water permeability in distended and undistended bladders, we found that distension appeared to enhance ADH-stimulated water flow by decreasing the resistance of the series permeability barrier while the apparent water permeability associated with each single luminal membrane aggregate was unaffected. In that bladder distension caused tissue thinning, the series resistance limiting ADH-stimulated water flow appears to be accounted for by deformable barriers within the bladder tissue itself, probably unstirred layers of water.
我们最近描述了一种方法，通过该方法可以将抗利尿激素刺激的蟾蜍膀胱腔膜对水流的阻力与与其串联的屏障的阻力进行定量区分。该方法需要估计膀胱总水渗透性（通过在恒定梯度下的跨膀胱渗透水流评估）和腔膜水渗透性（通过定量抗利尿激素诱导的腔膜颗粒聚集频率评估）。在本研究中，我们检查了膀胱扩张对最大抗利尿激素刺激之前和期间跨上皮渗透水流的影响。基线水流不受膀胱扩张的影响，但随着膀胱扩张程度增加，激素刺激的水流系统性增加。扩张对抗利尿激素诱导的膜内颗粒聚集频率没有影响。通过比较扩张和未扩张膀胱中聚集频率与激素诱导的水渗透性之间的关系，我们发现扩张似乎通过降低串联渗透屏障的阻力来增强抗利尿激素刺激的水流，而与每个单个腔膜聚集相关的表观水渗透性不受影响。由于膀胱扩张导致组织变薄，限制抗利尿激素刺激水流的串联阻力似乎由膀胱组织本身内的可变形屏障引起，可能是未搅动的水层。
