title: Salt sensitivity of renin secretion, glomerular filtration rate and blood pressure in conscious Sprague-Dawley rats.
abstract: OBJECTIVE
  We hypothesized that in normal rats in metabolic steady state, (i) the plasma renin concentration (PRC) is log-linearly related to Na(+) intake (NaI), (ii) the concurrent changes in mean arterial pressure (MABP) and glomerular filtration rate (GFR) are negligible and (iii) the function PRC = f(NaI) is altered by β₁-adrenoceptor blockade (metoprolol) and surgical renal denervation (DNX).
  
  
  METHODS
  In catheterized, conscious rats on low-Na(+) diet (0.004% Na(+)), NaI was increased by up to 120-fold, in four 3-day steps, by intravenous saline infusion. MABP was recorded continuously, PRC measured in arterial blood, and GFR estimated by inulin clearance.
  
  
  RESULTS
  Steady states were achieved within 3 days. PRC [mIU L(-1)] was log-linearly related to NaI [mmol kg(-1) day(-1)]: PRC = -9.9 log (NaI) + 22. Set point (22 mIU L(-1) at NaI = 1) and slope (9.9 mIU per decade NaI) were independent of metoprolol administration and DNX. MABP and GFR were markedly salt-sensitive: MABP [mmHg] = 4.9 log (NaI) + 99 (P < 0.01), and GFR [mL min(-1)] = 1.4 log (NaI) + 8.3 (P < 0.01). MABP increased similarly (approx. 10%, P < 0.001) irrespective of pre-treatment. Metoprolol, but not DNX, reduced MABP, HR, and GFR (all P < 0.01). Salt sensitivity of GFR was not observed in DNX rats.
  
  
  CONCLUSIONS
  Log-linear relations to sodium intake exist not only for PRC, but also for MABP and GFR, which per 10-fold increase in sodium intake rose by 5 mmHg and 1.4 mL min(-1) respectively. Steady-state levels of PRC appear independent of renal nerves. MABP and GFR seem markedly salt sensitive in normal rats.
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark.
authors.forename: G L
authors.initials: GL
authors.lastname: Isaksson
authors.forename: J
authors.initials: J
authors.lastname: Stubbe
authors.forename: P
authors.initials: P
authors.lastname: Lyngs Hansen
authors.forename: B L
authors.initials: BL
authors.lastname: Jensen
authors.forename: P
authors.initials: P
authors.lastname: Bie
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D003243:Consciousness; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000097:blood* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012965:Sodium Chloride / Q000378:metabolism*
chemical_list: D012965:Sodium Chloride; D012083:Renin
keywords: Sprague Dawley; blood pressure; glomerular filtration rate; renin; salt sensitivity