title: AT1a receptor signaling is required for basal and water deprivation-induced urine concentration in AT1a receptor-deficient mice.
abstract: It is well recognized that ANG II interacts with arginine vasopressin (AVP) to regulate water reabsorption and urine concentration in the kidney. The present study used ANG II type 1a (AT(1a)) receptor-deficient (Agtr1a(-/-)) mice to test the hypothesis that AT(1a) receptor signaling is required for basal and water deprivation-induced urine concentration in the renal medulla. Eight groups of wild-type (WT) and Agtr1a(-/-) mice were treated with or without 24-h water deprivation and 1-desamino-8-d-AVP (DDAVP; 100 ng/h ip) for 2 wk or with losartan (10 mg/kg ip) during water deprivation. Under basal conditions, Agtr1a(-/-) mice had lower systolic blood pressure (P < 0.01), greater than threefold higher 24-h urine excretion (WT mice: 1.3 ± 0.1 ml vs. Agtr1a(-/-) mice: 5.9 ± 0.7 ml, P < 0.01), and markedly decreased urine osmolality (WT mice: 1,834 ± 86 mosM/kg vs. Agtr1a(-/-) mice: 843 ± 170 mosM/kg, P < 0.01), without significant changes in 24-h urinary Na(+) excretion. These responses in Agtr1a(-/-) mice were associated with lower basal plasma AVP (WT mice: 105 ± 8 pg/ml vs. Agtr1a(-/-) mice: 67 ± 6 pg/ml, P < 0.01) and decreases in total lysate and membrane aquaporin-2 (AQP2; 48.6 ± 7% of WT mice, P < 0.001) and adenylyl cyclase isoform III (55.6 ± 8% of WT mice, P < 0.01) proteins. Although 24-h water deprivation increased plasma AVP to the same levels in both strains, 24-h urine excretion was still higher, whereas urine osmolality remained lower, in Agtr1a(-/-) mice (P < 0.01). Water deprivation increased total lysate AQP2 proteins in the inner medulla but had no effect on adenylyl cyclase III, phosphorylated MAPK ERK1/2, and membrane AQP2 proteins in Agtr1a(-/-) mice. Furthermore, infusion of DDAVP for 2 wk was unable to correct the urine-concentrating defects in Agtr1a(-/-) mice. These results demonstrate that AT(1a) receptor-mediated ANG II signaling is required to maintain tonic AVP release and regulate V(2) receptor-mediated responses to water deprivation in the inner medulla.
authors: Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of MississippiMedical Center, 2500 N. State St., Jackson, MS 39216-4505, USA.
authors: Xiao C
authors: XC
authors: Li
authors: Yuan
authors: Y
authors: Shao
authors: Jia L
authors: JL
authors: Zhuo
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D051399:Aquaporin 2 / Q000378:metabolism; D001127:Arginine Vasopressin / Q000097:blood; D001794:Blood Pressure; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D019808:Losartan / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D051379:Mice; D009994:Osmolar Concentration; D044140:Receptor, Angiotensin, Type 1 / Q000172:deficiency* / Q000502:physiology*; D014868:Water Deprivation
chemical_list: C544066:Agtr1a protein, mouse; C496024:Aqp2 protein, mouse; D051399:Aquaporin 2; D044140:Receptor, Angiotensin, Type 1; D001127:Arginine Vasopressin; D000262:Adenylyl Cyclases; C421784:adenylate cyclase 3; D003894:Deamino Arginine Vasopressin; D019808:Losartan