title: Nitric oxide, prostaglandins and angiotensin II in the regulation of renal medullary blood flow during volume expansion.
abstract: Regulation of medullary blood flow (MBF) is essential in maintaining renal function and blood pressure. However, it is unknown whether outer MBF (OMBF) and papillary blood flow (PBF) are regulated independently when extracellular volume (ECV) is enhanced. The aim of this study was to determine whether OMBF and PBF are differently regulated and whether there is an interaction between nitric oxide (NO), prostaglandins (PGs) and angiotensin II (Ang II) in regulating OMBF and PBF when ECV is enhanced. To achieve these goals, OMBF and PBF were measured by laser-Doppler in volume-expanded rats treated with a cyclooxygenase inhibitor (meclofenamate, 3 mg/kg) and/or a NO synthesis inhibitor (L-nitro-arginine methyl ester (L-NAME), 3 μg/kg/min) and/or Ang II (10 ng/kg/min). OMBF was unchanged by NO or PGs synthesis inhibition but decreased by 36 % (P < 0.05) when L-NAME and meclofenamate were infused simultaneously. PBF was similarly reduced by L-NAME (12 %), meclofenamate (17 %) or L-NAME + meclofenamate (19 %). Ang II did not modify OMBF, but it led to a similar decrease (P < 0.05) in OMBF when it was administered to rats with reduced NO (32 %), PGs (36 %) or NO and PGs (37 %) synthesis. In contrast, the fall in PBF induced by Ang II (12 %) was enhanced (P < 0.05) by the simultaneous PGs (30 %) or PGs and NO (31 %) synthesis inhibition but not in L-NAME-treated rats (20 %). This study presents novel findings suggesting that blood flows to the outer medulla and renal papilla are differently regulated and showing that there is a complex interaction between NO, PGs and Ang II in regulating OMBF and PBF when ECV is enhanced.
authors.affiliation: Cardiovascular and Metabolic Diseases, MedImmune, Cambridge, UK.
authors.forename: Carol
authors.initials: C
authors.lastname: Moreno
authors.affiliation: Department of Physiology, School of Medicine, University of Murcia, Murcia, 30100, Spain.|Regional Campus of International Excellence "Mare Nostrum", Murcia, Spain.|Instituto Murciano de Investigación Biomédica, Murcia, Spain.
authors.forename: María T
authors.initials: MT
authors.lastname: Llinás
authors.affiliation: Department of Physiology, School of Medicine, University of Murcia, Murcia, 30100, Spain.|Regional Campus of International Excellence "Mare Nostrum", Murcia, Spain.|Instituto Murciano de Investigación Biomédica, Murcia, Spain.
authors.forename: Francisca
authors.initials: F
authors.lastname: Rodriguez
authors.affiliation: Department of Physiology, School of Medicine, University of Murcia, Murcia, 30100, Spain.|Regional Campus of International Excellence "Mare Nostrum", Murcia, Spain.|Instituto Murciano de Investigación Biomédica, Murcia, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Moreno
authors.affiliation: Department of Physiology, School of Medicine, University of Murcia, Murcia, 30100, Spain. salazar@um.es.|Regional Campus of International Excellence "Mare Nostrum", Murcia, Spain. salazar@um.es.|Instituto Murciano de Investigación Biomédica, Murcia, Spain. salazar@um.es.
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Salazar
mesh_terms: D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D005919:Glomerular Filtration Rate; D007679:Kidney Medulla / Q000098:blood supply*; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D011453:Prostaglandins / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000502:physiology*
chemical_list: D011453:Prostaglandins; D000804:Angiotensin II; D009569:Nitric Oxide
keywords: Angiotensin II; L-NAME; Laser-Doppler; Meclofenamate; Renal medulla; Volume expansion