title: Angiotensin II facilitates autoregulation in the perfused mouse kidney: An optimized in vitro model for assessment of renal vascular and tubular function.
abstract: OBJECTIVE
  We have optimized the isolated perfused mouse kidney (IPMK) model for studying renal vascular and tubular function in vitro using 24-28 g C57BL6J mice; the wild type controls for many transgenic mice.
  
  
  RESULTS
  Buffer composition was optimized for bovine serum albumin concentration (BSA). The effect of adding erythrocytes on renal function and morphology was assessed. Autoregulation was investigated during stepped increases in perfusion pressure. Perfusion for 60 min at 90-110 mmHg with Krebs bicarbonate buffer containing 5.5% BSA, and amino acids produced functional parameters within the in vivo range. Erythrocytes increased renal vascular resistance (3.8 +/- 0.2 vs 2.4 +/- 0.1 mL/min.mmHg, P < 0.05), enhanced sodium reabsorption (FE(Na) = 0.3 +/- 0.08 vs 1.5 +/- 0.7%, P < 0.05), produced equivalent glomerular filtration rates (GFR; 364 +/- 38 vs 400 +/- 9 microL/min per gkw) and reduced distal tubular cell injury in the inner stripe (5.8 +/- 1.7 vs 23.7 +/- 3.1%, P < 0.001) compared to cell free perfusion. The IPMK was responsive to vasoconstrictor (angiotensin II, EC50 100 pM) and vasodilator (methacholine, EC50 75 nM) mediators and showed partial autoregulation of perfusate flow under control conditions over 65-85 mmHg; autoregulatory index (ARI) of 0.66 +/- 0.11. Angiotensin II (100 pM) extended this range (to 65-120 mmHg) and enhanced efficiency (ARI 0.21 +/- 0.02, P < 0.05). Angiotensin II facilitation was antagonized by methacholine (ARI 0.76 +/- 0.08) and papaverine (ARI 0.91 +/- 0.13).
  
  
  CONCLUSIONS
  The IPMK model is useful for studying renal physiology and pathophysiology without systemic neurohormonal influences.
authors.affiliation: Department of Medicine, Central Clinical Division, School of Medicine, University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Majid
authors.initials: M
authors.lastname: Rahgozar
authors.forename: Zhengrong
authors.initials: Z
authors.lastname: Guan
authors.forename: Anita
authors.initials: A
authors.lastname: Matthias
authors.forename: Glenda C
authors.initials: GC
authors.lastname: Gobé
authors.forename: Zoltán H
authors.initials: ZH
authors.lastname: Endre
mesh_terms: D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D005919:Glomerular Filtration Rate; D006706:Homeostasis; D066298:In Vitro Techniques; D007668:Kidney / Q000098:blood supply* / Q000502:physiology*; D007684:Kidney Tubules / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010477:Perfusion
chemical_list: D000804:Angiotensin II