Abstract：
We have previously shown that kidney collecting ducts make vasopressin. However, the physiological role of collecting duct-derived vasopressin is uncertain. We hypothesized that collecting duct-derived vasopressin is required for the appropriate concentration of urine. We developed a vasopressin conditional knockout (KO) mouse model wherein Cre recombinase expression induces deletion of arginine vasopressin (Avp) exon 1 in the distal nephron. We then used age-matched 8- to 12-wk-old Avp fl/fl;Ksp-Cre(-) [wild type (WT)] and Avp fl/fl;Ksp-Cre(+) mice for all experiments. We collected urine, serum, and kidney lysates at baseline. We then challenged both WT and knockout (KO) mice with 24-h water restriction, water loading, and administration of the vasopressin type 2 receptor agonist desmopressin (1 µg/kg ip) followed by the vasopressin type 2 receptor antagonist OPC-31260 (10 mg/kg ip). We performed immunofluorescence and immunoblot analysis at baseline and confirmed vasopressin KO in the collecting duct. We found that urinary osmolality (UOsm), plasma Na+, K+, Cl-, blood urea nitrogen, and copeptin were similar in WT vs. KO mice at baseline. Immunoblots of the vasopressin-regulated proteins Na+-K+-2Cl- cotransporter, NaCl cotransporter, and water channel aquaporin-2 showed no difference in expression or phosphorylation at baseline. Following 24-h water restriction, WT and KO mice had no differences in UOsm, plasma Na+, K+, Cl-, blood urea nitrogen, or copeptin. In addition, there were no differences in the rate of urinary concentration or dilution as in WT and KO mice UOsm was nearly identical after desmopressin and OPC-31260 administration. We conclude that collecting duct-derived vasopressin is not essential to appropriately concentrate or dilute urine.NEW & NOTEWORTHY Hypothalamic vasopressin is required for appropriate urinary concentration. However, whether collecting duct-derived vasopressin is involved remains unknown. We developed a novel transgenic mouse model to induce tissue-specific deletion of vasopressin and showed that collecting duct-derived vasopressin is not required to concentrate or dilute urine.
摘要：
我们以前证明肾脏集合管会产生加压素。然而,收集管源性血管加压素的生理作用尚不确定.我们假设适当的尿液浓度需要收集管衍生的加压素。我们开发了加压素条件性敲除小鼠模型，其中Cre重组酶表达诱导远端肾单位中Avp外显子1的缺失。然后我们使用年龄匹配的8-12周龄Avpfl/fl;Ksp-Cre(-)(WT)和Avpfl/fl;Ksp-Cre(+)小鼠进行所有实验。我们收集了尿液,血清,和基线时的肾脏裂解物。然后我们用24小时限水攻击WT和KO小鼠，装水,并施用2型加压素受体（V2R）激动剂去氨加压素（dDAVP）1µg/kg/ip），然后施用V2R拮抗剂OPC-31260（10mg/kg/ip）。我们在基线时进行了免疫荧光和免疫印迹分析，并确认了血管加压素在收集管中的敲除。我们发现尿渗透压(UOsm)，血浆Na+,K+,Cl-,BUN,和肽素在WT和KO小鼠的基线相似。加压素调节蛋白Na:K:2Cl协同转运蛋白(NKCC2)的免疫印迹,Na：Cl协同转运蛋白（NCC）和水通道水通道蛋白2（AQP2）在基线时的表达或磷酸化没有差异。在24小时限水之后，WT和KO小鼠的UOsm没有差异，血浆Na+,K+,Cl-,BUN或copeptin。此外,在dDAVP和OPC-31260给药后,由于WT和KO小鼠的UOsm几乎相同,因此尿液浓度或稀释率没有差异.我们得出的结论是，收集导管衍生的加压素对于适当浓缩或稀释尿液并不是必需的。
