Takahashi N, Chernavvsky D R, Gomez R A, Igarashi P, Gitelman H J, Smithies O
Department of Pathology and Laboratory Medicine and Division of Nephrology, University of North Carolina, Chapel Hill, NC 27599, USA.
Proc Natl Acad Sci U S A. 2000 May 9;97(10):5434-9. doi: 10.1073/pnas.090091297.
We have used homologous recombination to disrupt the mouse gene coding for the NaK2Cl cotransporter (NKCC2) expressed in kidney epithelial cells of the thick ascending limb and macula densa. This gene is one of several that when mutated causes Bartter's syndrome in humans, a syndrome characterized by severe polyuria and electrolyte imbalance. Homozygous NKCC2-/- pups were born in expected numbers and appeared normal. However, by day 1 they showed signs of extracellular volume depletion (hematocrit 51%; wild type 37%). They subsequently failed to thrive. By day 7, they were small and markedly dehydrated and exhibited renal insufficiency, high plasma potassium, metabolic acidosis, hydronephrosis of varying severity, and high plasma renin concentrations. None survived to weaning. Treatment of -/- pups with indomethacin from day 1 prevented growth retardation and 10% treated for 3 weeks survived, although as adults they exhibited severe polyuria (10 ml/day), extreme hydronephrosis, low plasma potassium, high blood pH, hypercalciuria, and proteinuria. Wild-type mice treated with furosemide, an inhibitor of NaK2Cl cotransporters, have a phenotype similar to the indomethacin-rescued -/- adults except that hydronephrosis was mild. The polyuria, hypercalciuria, and proteinuria of the -/- adults and furosemide-treated wild-type mice were unresponsive to inhibitors of the renin angiotensin system, vasopressin, and further indomethacin. Thus absence of NKCC2 in the mouse causes polyuria that is not compensated elsewhere in the nephron. The NKCC2 mutant animals should be valuable for uncovering new pathophysiologic and therapeutic aspects of genetic disturbances in water and electrolyte recovery by the kidney.
我们利用同源重组技术破坏了小鼠基因，该基因编码厚升支和致密斑肾上皮细胞中表达的钠钾氯共转运体（NKCC2）。该基因是人类中几个突变时会导致巴特综合征的基因之一，巴特综合征的特征是严重多尿和电解质失衡。纯合子NKCC2-/-幼崽出生数量符合预期且外观正常。然而，到第1天时，它们出现细胞外液量减少的迹象（血细胞比容为51%；野生型为37%）。随后它们生长不良。到第7天时，它们体型小且明显脱水，表现出肾功能不全、高血钾、代谢性酸中毒、不同程度的肾积水以及高血浆肾素浓度。无一存活至断奶。从第1天开始用吲哚美辛治疗-/-幼崽可防止生长迟缓，10%接受3周治疗的幼崽存活下来，不过成年后它们表现出严重多尿（10毫升/天）、极度肾积水、低血钾、高血pH值、高钙尿症和蛋白尿。用呋塞米（一种钠钾氯共转运体抑制剂）治疗的野生型小鼠具有与吲哚美辛挽救的-/-成年小鼠相似的表型，只是肾积水较轻。-/-成年小鼠和呋塞米治疗的野生型小鼠的多尿、高钙尿症和蛋白尿对肾素 - 血管紧张素系统抑制剂血管加压素以及进一步的吲哚美辛均无反应。因此，小鼠中NKCC2的缺失导致多尿，而肾单位其他部位无法代偿。NKCC2突变动物对于揭示肾脏水和电解质重吸收遗传紊乱的新病理生理学和治疗方面应该具有重要价值。
