Edwards B R, Harmanci M C
Ren Physiol. 1983;6(6):275-80. doi: 10.1159/000172912.
Despite the absence of vasopressin, Brattleboro homozygous (DI) rats can concentrate their urine to hypertonic levels when deprived of drinking water. When DI rats are infused with vasopressin, freeze-fracture electron microscopy has revealed increases in intramembranous particle clusters (IPC) in papillary collecting duct luminal membrane that parallel the rise in urine osmolality. In the present study, we examined whether the increase in concentrating ability of DI rats dehydrated for 24 h was associated with a change in IPC. For comparison, oral water loading and 24-hour dehydration were used to suppress and stimulate endogenous vasopressin secretion in Long-Evans (LE) rats, and the effects on urine osmolality and IPC were examined. In LE rats, the induced changes in water balance resulted in alterations in IPC frequency that paralleled urine osmolality, whereas, in DI rats, frequency of IPC remained low under all conditions, even when urine osmolality rose to almost 1,000 mosm/kg H2O as a result of 24-hour dehydration. These results suggest that the increased concentrating ability of dehydrated DI does not depend upon increased water permeability of the papillary collecting ducts.
尽管缺乏抗利尿激素，但当断水时，布拉德福德纯合子（尿崩症）大鼠仍能将尿液浓缩至高渗水平。给尿崩症大鼠输注抗利尿激素后，冷冻断裂电子显微镜检查显示，乳头集合管腔膜中的管状颗粒簇（IPC）增加，且与尿渗透压的升高平行。在本研究中，我们检测了脱水24小时的尿崩症大鼠浓缩能力的增加是否与IPC的变化有关。作为对照，通过给长-伊文斯（LE）大鼠口服水负荷和使其脱水24小时来抑制和刺激内源性抗利尿激素的分泌，并检测其对尿渗透压和IPC的影响。在LE大鼠中，诱导的水平衡变化导致IPC频率的改变，且与尿渗透压平行，而在尿崩症大鼠中，即使由于24小时脱水导致尿渗透压升至近1000 mosm/kg H₂O，在所有条件下IPC频率仍保持较低水平。这些结果表明，脱水尿崩症大鼠浓缩能力的增加并不依赖于乳头集合管水通透性的增加。
