title: Proximal tubular angiotensinogen in renal biopsy suggests nondipper BP rhythm accompanied by enhanced tubular sodium reabsorption.
abstract: OBJECTIVE
  The renal capacity for sodium excretion is impaired by a reduction in the glomerular ultrafiltration coefficient and by enhancement of the fractional tubular sodium reabsorption (FRNa), leading to a nondipper circadian blood pressure (BP) rhythm. Angiotensin II in the systemic circulation can be easily filtered across the glomerular capillary walls and stimulates renal proximal tubular angiotensinogen (PT-AGT) production, leading to the activation of intrarenal angiotensin II, which is known to augment the FRNa in animal models.
  
  
  METHODS
  We performed an immunohistochemical investigation to determine the contribution of PT-AGT to enhancement of FRNa and the nondipper circadian BP rhythm in 40 consecutive patients with primary IgA nephropathy (IgAN).
  
  
  RESULTS
  Immunostaining for PT-AGT was increased in the IgAN patients compared with control individuals (P = 0.04), and correlated directly with the FRNa (r = 0.39, P = 0.01) and the night/day ratio of BP (r = 0.38, P = 0.02), but not creatinine clearance (r = -0.008, P = 0.9). The night/day ratio of BP was determined by both creatinine clearance (r = -0.36, P = 0.03) and FRNa (r = 0.47, P = 0.006).
  
  
  CONCLUSIONS
  Tubular sodium reabsorption is stimulated by intrarenal angiotensin II, as indicated by PT-AGT, and contributes to the genesis of the nondipper BP rhythm. Further studies are needed to evaluate whether or not treatment to prevent sodium retention is useful for patients who exhibit increased PT-AGT in renal biopsies.
authors.affiliation: Department of Cardio-Renal Medicine and Hypertension, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan. m-fukuda@med.nagoya-cu.ac.jp
authors.forename: Michio
authors.initials: M
authors.lastname: Fukuda
authors.forename: Maki
authors.initials: M
authors.lastname: Urushihara
authors.forename: Tamaki
authors.initials: T
authors.lastname: Wakamatsu
authors.forename: Tadashi
authors.initials: T
authors.lastname: Oikawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kobori
mesh_terms: D000808:Angiotensinogen / Q000378:metabolism*; D001706:Biopsy; D001794:Blood Pressure; D005260:Female; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012964:Sodium / Q000378:metabolism*
chemical_list: D000808:Angiotensinogen; D012964:Sodium