Yamamoto T, Sasaki S, Fushimi K, Kawasaki K, Yaoita E, Oota K, Hirata Y, Marumo F, Kihara I
Department of Pathology, Niigata University School of Medicine, Japan.
Exp Nephrol. 1995 May-Jun;3(3):193-201.
The cellular and subcellular localization and expression of a kidney collecting duct water channel, aquaporin (AQP)-CD, were examined in the kidneys of hydrated and dehydrated rats by immunostaining, Northern blot analysis, and radioimmunoassay. In hydrated rat kidneys, AQP-CD was selectively found in the collecting duct principal cells and inner medullary collecting duct cells, but not in the intercalated cells. At a light microscopic level, AQP-CD was diffusely present in a granular pattern throughout the cytoplasm of the collecting duct cells with a preferential accumulation in subapical regions. By immunoelectron microscopy, AQP-CD was frequently demonstrated along membranes of small vesicles in the subapical cytoplasm and occasionally along the basolateral membranes of these cells. However, immunolabeling was sparse on the apical membranes. In dehydrated rats, AQP-CD immunostaining was intensified in the subapical cytoplasm of the collecting duct cells, along with increases in the number and size of AQP-CD-bearing vesicles in the subapical regions and with increment of labeling along the apical membranes. The increase in the amount of AQP-CD in the collecting duct cells of dehydrated rat kidneys was quantitatively confirmed by elevation of AQP-CD at mRNA and protein levels. The AQP-CD localization is consistent with the predicted site of the antidiuretic hormone (ADH)-regulated water channel in the collecting ducts and the increase in AQP-CD at mRNA and protein levels by dehydration may account for high concentration of urine in dehydrated subjects.
通过免疫染色、Northern印迹分析和放射免疫测定法，对水合及脱水大鼠肾脏中一种肾集合管水通道——水通道蛋白（AQP）-CD的细胞及亚细胞定位和表达进行了检测。在水合大鼠肾脏中，AQP-CD选择性地存在于集合管主细胞和内髓集合管细胞中，而不存在于闰细胞中。在光学显微镜水平，AQP-CD以颗粒状弥漫分布于集合管细胞的整个细胞质中，且优先聚集于顶端下区域。通过免疫电子显微镜观察，AQP-CD常见于顶端下细胞质中小泡的膜上，偶尔也见于这些细胞的基底外侧膜上。然而，顶端膜上的免疫标记很稀疏。在脱水大鼠中，集合管细胞顶端下细胞质中的AQP-CD免疫染色增强，同时顶端下区域中含AQP-CD小泡的数量和大小增加，且顶端膜上的标记增多。脱水大鼠肾脏集合管细胞中AQP-CD量的增加通过mRNA和蛋白质水平上AQP-CD的升高得到了定量证实。AQP-CD的定位与抗利尿激素（ADH）调节的集合管水通道的预测位点一致，脱水导致的AQP-CD在mRNA和蛋白质水平上的增加可能解释了脱水受试者尿液的高浓度。
