Loss of vitamin D receptor produces polyuria by increasing thirst.
Vitamin D receptor (VDR)-null mice develop polyuria, but the underlying mechanism remains unknown. In this study, we investigated the relationship between vitamin D and homeostasis of water and electrolytes. VDR-null mice had polyuria, but the urine osmolarity was normal as a result of high salt excretion. The urinary responses to water restriction and to vasopressin were similar between wild-type and VDR-null mice, suggesting intact fluid-handling capacity in VDR-null mice. Compared with wild-type mice, however, renin and angiotensin II were dramatically upregulated in the kidney and brain of VDR-null mice, leading to a marked increase in water intake and salt appetite. Angiotensin II-mediated upregulation of intestinal NHE3 expression partially explained the increased salt absorption and excretion in VDR-null mice. In the brain of VDR-null mice, expression of c-Fos, which is known to associate with increased water intake, was increased in the hypothalamic paraventricular nucleus and the subfornical organ. Treatment with an angiotensin II type 1 receptor antagonist normalized water intake, urinary volume, and c-Fos expression in VDR-null mice. Furthermore, despite a salt-deficient diet to reduce intestinal salt absorption, VDR-null mice still maintained the increased water intake and urinary output. Together, these data indicate that the polyuria observed in VDR-null mice is not caused by impaired renal fluid handling or increased intestinal salt absorption but rather is the result of increased water intake induced by the increase in systemic and brain angiotensin II.
Kong
Juan
J
Department of Medicine and Committee on Molecular Metabolism and Nutrition, University of Chicago, Chicago, IL 60637, USA.
Zhang
Zhongyi
Z
Li
Dongdong
D
Wong
Kari E
KE
Zhang
Yan
Y
Szeto
Frances L
FL
Musch
Mark W
MW
Li
Yan Chun
YC
D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D005786:Gene Expression Regulation; D019808:Losartan / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D011141:Polyuria / Q000209:etiology / Q000235:genetics* / Q000473:pathology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000235:genetics* / Q000502:physiology*; D012083:Renin / Q000097:blood; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012492:Salts / Q000494:pharmacology; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013894:Thirst; D015854:Up-Regulation
D016760:Proto-Oncogene Proteins c-fos; D018167:Receptors, Calcitriol; D012492:Salts; C000613386:Slc9a3 protein, mouse; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D000804:Angiotensin II; D012083:Renin; D019808:Losartan