Dept. of Medical Research, Holstebro Hospital, Holstebro, Denmark.
Am J Physiol Renal Physiol. 2012 Jan 15;302(2):F264-75. doi: 10.1152/ajprenal.00442.2010. Epub 2011 Oct 12.
The degree of water transport via aquaporin-2 (AQP2) water channels in renal collecting duct principal cells is reflected by the level of the urinary excretion of AQP2 (u-AQP2). In rats, the AQP2 expression varies with sodium intake. In humans, the effect of sodium intake on u-AQP2 and the underlying mechanisms have not previously been studied. We measured the effect of 4 days of high sodium (HS) intake (300 mmol sodium/day; 17.5 g salt/day) and 4 days of low sodium (LS) intake (30 mmol sodium/day; 1.8 g salt/day) on u-AQP2, fractional sodium excretion (FE(Na)), free water clearance (C(H2O)), urinary excretion of PGE(2) (u-PGE(2)) and cAMP (u-cAMP), and plasma concentrations of vasopressin (AVP), renin (PRC), ANG II, aldosterone (Aldo), atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) in a randomized, crossover study of 21 healthy subjects, during 24-h urine collection and after hypertonic saline infusion. The 24-h urinary sodium excretion was significantly higher during HS intake (213 vs. 41 mmol/24 h). ANP and BNP were significantly lower and PRC, ANG II, and Aldo were significantly higher during LS intake. AVP, u-cAMP, and u-PGE(2) were similar during HS and LS intake, but u-AQP2 was significantly higher during HS intake. The increases in AVP and u-AQP2 in response to hypertonic saline infusion were similar during HS and LS intake. In conclusion, u-AQP2 was increased during HS intake, indicating that water transport via AQP2 was increased. The effect was mediated by an unknown AVP-independent mechanism.
水通道蛋白-2（AQP2）水通道在肾集合管主细胞中的水转运程度反映在 AQP2 的尿排泄水平（u-AQP2）上。在大鼠中，AQP2 的表达随钠摄入量而变化。在人类中，钠摄入量对 u-AQP2 的影响及其潜在机制尚未得到研究。我们测量了高钠（HS）摄入（300mmol 钠/天；17.5g 盐/天）和低钠（LS）摄入（30mmol 钠/天；1.8g 盐/天）对 u-AQP2、钠分数排泄（FE（Na））、自由水清除率（C（H2O））、前列腺素 E2（u-PGE2）和 cAMP（u-cAMP）的尿排泄以及血管加压素（AVP）、肾素（PRC）、血管紧张素 II（ANG II）、醛固酮（Aldo）、心房利钠肽（ANP）和脑利钠肽（BNP）的血浆浓度的影响，在 21 名健康受试者的随机交叉研究中，在 24 小时尿液收集和高渗盐水输注后进行。HS 摄入时 24 小时尿钠排泄明显增加（213 与 41mmol/24h）。LS 摄入时，ANP 和 BNP 明显降低，PRC、ANG II 和 Aldo 明显升高。HS 和 LS 摄入时，AVP、u-cAMP 和 u-PGE2 相似，但 HS 摄入时 u-AQP2 明显升高。高渗盐水输注引起的 AVP 和 u-AQP2 增加在 HS 和 LS 摄入时相似。总之，HS 摄入时 u-AQP2 增加，表明 AQP2 介导的水转运增加。这种作用是由未知的 AVP 独立机制介导的。
