Palmer L G, Speez N
Am J Physiol. 1984 Apr;246(4 Pt 2):F501-8. doi: 10.1152/ajprenal.1984.246.4.F501.
To test the hypothesis that antidiuretic hormone- (ADH) dependent water permeability is associated with changes in apical membrane area, hormone-dependent water flow and capacitance changes were measured in the toad urinary bladder under a number of different conditions. Dose-response relationships for water flow (Jv) and capacitance increases (delta C) were similar from 1 to 20 mU/ml ADH. At higher concentrations, Jv reached a plateau, while delta C decreased. The decrease in delta C was prevented by elimination of the osmotic gradient across the tissue. Serosal hydrazine (10 mM) increased Jv sevenfold and delta C threefold in the presence of 1 mU/ml ADH. Mucosal NH4Cl, at constant mucosal pH, increased Jv by 50-100%, but did not significantly change delta C. In the absence of an osmotic gradient, mucosal NH+4 increased delta C by 50%. NH4Cl had no effect on hydroosmotic response to 8-bromo-adenosine 3',5'-cyclic monophosphate (cAMP). Mucosal CO2 (9%) decreased Jv by greater than 90%, and delta C by 60% with 20 mU/ml ADH. Mucosal CO2 also inhibited the hydroosmotic response to 8-bromo-cAMP. Removal of serosal Na diminished cAMP-dependent Jv and delta C. The results confirmed the close relationship between ADH-dependent water permeability and membrane capacitance. They indicate, however, that under some circumstances membrane may be retrieved from the apical surface without affecting water permeability.
为了验证抗利尿激素（ADH）依赖性水通透性与顶端膜面积变化相关的假说，在多种不同条件下，对蟾蜍膀胱中激素依赖性水流量和电容变化进行了测量。从1至20 mU/ml的ADH，水流量（Jv）和电容增加（δC）的剂量反应关系相似。在更高浓度时，Jv达到平台期，而δC下降。通过消除组织两侧的渗透梯度可防止δC的下降。在存在1 mU/ml ADH的情况下，浆膜肼（10 mM）使Jv增加了7倍，δC增加了3倍。在黏膜pH恒定的情况下，黏膜NH4Cl使Jv增加了50 - 100%，但对δC没有显著影响。在没有渗透梯度的情况下，黏膜NH4+使δC增加了50%。NH4Cl对8 - 溴腺苷3'，5'-环磷酸（cAMP）的水渗透反应没有影响。黏膜CO2（9%）使20 mU/ml ADH时的Jv下降超过90%，δC下降60%。黏膜CO2也抑制了对8 - 溴cAMP的水渗透反应。去除浆膜Na会降低cAMP依赖性的Jv和δC。结果证实了ADH依赖性水通透性与膜电容之间的密切关系。然而，结果表明在某些情况下，膜可能从顶端表面回收而不影响水通透性。
