Saito T, Ishikawa S, Sasaki S, Higashiyama M, Nagasaka S, Fujita N, Fushimi K, Marumo F
Division of Endocrinology and Metabolism, Department of Medicine, Jichi Medical School, Tochigi 329-0498, Japan.
Am J Physiol. 1999 Aug;277(2):R427-33. doi: 10.1152/ajpregu.1999.277.2.R427.
Arginine vasopressin (AVP) plays an important role in the expression of aquaporin (AQP-2) in the collecting duct. The present study was undertaken to determine whether there is an AVP-independent regulation of AQP-2 gene expression in homozygous Brattleboro rats in which endogenous AVP is absent. Exogenous administration of 1-deamino-8-D-AVP produced an antidiuresis and expressed AQP-2 mRNA and AQP-2 protein in the renal medulla of the homozygous Brattleboro rats. Twelve hours of water deprivation produced severe dehydration in the homozygous Brattleboro rats, such that urinary osmolality increased from 200 to 649 mosmol/kgH(2)O. However, no increase in AQP-2 mRNA expression was observed after this dehydration, and the medullary tissue content and urinary excretion of AQP-2 also remained unchanged. Increases in AQP-2 mRNA expression and AQP-2 protein were evident in Long-Evans rats after 64 h of water deprivation, with a severity of dehydration almost equal to the 12-h dehydrated, homozygous Brattleboro rats. These results indicate the lack of an AVP-independent mechanism for upregulating AQP-2 mRNA expression in renal collecting duct cells.
精氨酸加压素（AVP）在集合管水通道蛋白（AQP - 2）的表达中起重要作用。本研究旨在确定在缺乏内源性AVP的纯合布拉特洛维大鼠中，是否存在不依赖AVP的AQP - 2基因表达调控机制。向纯合布拉特洛维大鼠外源性给予1 - 去氨基 - 8 - D - AVP可产生抗利尿作用，并在其肾髓质中表达AQP - 2 mRNA和AQP - 2蛋白。对纯合布拉特洛维大鼠进行12小时禁水导致严重脱水，尿渗透压从200 mosmol/kgH₂O升高至649 mosmol/kgH₂O。然而，这种脱水后未观察到AQP - 2 mRNA表达增加，且AQP - 2的髓质组织含量和尿排泄量也保持不变。在禁水64小时后的长 - 伊文斯大鼠中，AQP - 2 mRNA表达和AQP - 2蛋白明显增加，其脱水严重程度几乎与禁水12小时的纯合布拉特洛维大鼠相同。这些结果表明，肾集合管细胞中缺乏上调AQP - 2 mRNA表达的不依赖AVP的机制。
