The contribution of collecting duct NOS1 to the concentrating mechanisms in male and female mice

Abstract

The collecting duct (CD) concentrates the urine, thereby maintaining body water volume and plasma osmolality within a normal range. The endocrine hormone arginine vasopressin acts in the CD to increase water permeability via the vasopressin 2 receptor (V2R)-aquaporin (AQP) axis. Recent studies have suggested that autocrine factors may also contribute to the regulation of CD water permeability. Nitric oxide is produced predominantly by nitric oxide synthase 1 (NOS1) in the CD and acts as a diuretic during salt loading. The present study sought to determine whether CD NOS1 regulates diuresis during changes in hydration status. Male and female control and CD NOS1 knockout (CDNOS1KO) mice were hydrated (5% sucrose water), water deprived, or acutely challenged with the V2R agonist desmopressin. In male mice, water deprivation resulted in decreased urine flow and increased plasma osmolality, copeptin concentration, and kidney AQP2 abundance independent of CD NOS1. In female control mice, water deprivation reduced urine flow, increased plasma osmolality and copeptin, but did not significantly change total AQP2; however, there was increased basolateral AQP3 localization. Surprisingly, female CDNOS1KO mice while on the sucrose water presented with symptoms of dehydration. Fibroblast growth factor 21, an endocrine regulator of sweetness preference, was significantly higher in female CDNOS1KO mice, suggesting that this was reducing their drive to drink the sucrose water. With acute desmopressin challenge, female CDNOS1KO mice failed to appropriately concentrate their urine, resulting in higher plasma osmolality than controls. In conclusion, CD NOS1 plays only a minor role in urine-concentrating mechanisms.

Loss of circadian geneBmal1in the collecting duct lowers blood pressure in male, but not female, mice

“…There appeared to be a trace amount of recombined DNA in the cortex, but none was detected in tissue from the tail or liver. Since recent studies have shown that AQP2-Cre can be detected in certain parts of the mouse brain (21,25), we also dissected mouse brain and extracted DNA from the frontal cortex, brain stem, hypothalamus, and cerebellum. In similar previous reports, we detected recombined alleles in the brain cortex and hypothalamus (Fig.…”

Rapid development of vasopressin resistance in dietary K+ deficiency

“…Pharmaceutical-grade desmopressin (DDAVP) was dissolved in 0.9% saline solution and administered via intraperitoneal injection at 10 ng in 100 mL of saline via intraperitoneal injection (34). Mice were treated with DDAVP on day 8 of K þ deprivation.…”

Role of collecting duct principal cell NOS1β in sodium and potassium homeostasis

“…All animal use and welfare adhered to the NIH Guide for the Care and Use of Laboratory Animals following a protocol reviewed and approved by the Institutional Laboratory Animal Care and Use Committees of the University of Alabama at Birmingham (UAB) or the Medical College of Wisconsin. Principal cell, CD‐specific NOS1 knockout male mice ( Aqp2 ‐CRE with Nos1 flox / flox ; CDNOS1KO) and littermate controls ( Nos1 flox / flox ) from the colony maintained at UAB were used (Hyndman et al, 2013 , 2015 , 2017 ; Mendoza & Hyndman, 2019 ). Only male mice were used because our previous publications have established that male CDNOS1KO mice have salt‐sensitive increases in blood pressure and inappropriate ENaC activation (Hyndman et al, 2013 , 2015 , 2017 ).…”

“…All mice were weaned on NIH‐31 diet (Envigo; 7017 (irradiated), 0.3% Na + , 0.6% K + ) and were used in the study at 12–20 weeks of age. Homozygous NOS1 flox/flox mice were used as controls and CDNOS1KO mice genotypes were confirmed as previously described (Hyndman et al, 2013 , 2015 , 2017 ; Mendoza & Hyndman, 2019 ). Mice were group‐housed with standard bedding and nesting sheets for enrichment in an animal facility with a 12 h light: 12 h dark cycle.…”

“…Western blots were performed with kidney cortical homogenates as previously described in detail (Hyndman et al, 2017 ; Mendoza & Hyndman, 2019 ). The primary antibodies for K ir 4.1 (ab105102, lot GR1925047, a goat polyclonal, Abcam) and K ir 5.1 (ab74130, lot GR259059‐2, a rabbit polyclonal, Abcam) were used at a 1/1000 dilution and were previously validated against rat knockout tissues (Palygin, Levchenko, et al, 2017 ; Palygin, Pochynyuk, et al, 2017 ).…”