title: The influence of nitric oxide synthase 1 on blood flow and interstitial nitric oxide in the kidney.
abstract: The role of nitric oxide (NO) produced by NO synthase 1 (NOS1) in the renal vasculature remains undetermined. In the present study, we investigated the influence of systemic inhibition of NOS1 by intravenous administration of N(omega)-propyl-L-arginine (L-NPA; 1 mg. kg(-1). h(-1)) and N(5)-(1-imino-3-butenyl)-L-ornithine (v-NIO; 1 mg. kg(-1). h(-1)), highly selective NOS1 inhibitors, on renal cortical and medullary blood flow and interstitial NO concentration in Sprague-Dawley rats. Arterial blood pressure was significantly decreased by administration of both NOS1-selective inhibitors (-11 +/- 1 mmHg with L-NPA and -7 +/- 1 mmHg with v-NIO; n = 9/group). Laser-Doppler flowmetry experiments demonstrated that blood flow in the renal cortex and medulla was not significantly altered following administration of either NOS1-selective inhibitor. In contrast, the renal interstitial level of NO assessed by an in vivo microdialysis oxyhemoglobin-trapping technique was significantly decreased in both the renal cortex (by 36-42%) and medulla (by 32-40%) following administration of L-NPA (n = 8) or v-NIO (n = 8). Subsequent infusion of the nonspecific NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME; 50 mg. kg(-1). h(-1)) to rats pretreated with either of the NOS1-selective inhibitors significantly increased mean arterial pressure by 38-45 mmHg and significantly decreased cortical (25-29%) and medullary (37-43%) blood flow. In addition, L-NAME further decreased NO in the renal cortex (73-77%) and medulla (62-71%). To determine if a 40% decrease in NO could alter renal blood flow, a lower dose of L-NAME (5 mg. kg(-1). h(-1); n = 8) was administered to a separate group of rats. The low dose of L-NAME reduced interstitial NO (cortex 39%, medulla 38%) and significantly decreased blood flow (cortex 23-24%, medulla 31-33%). These results suggest that NOS1 does not regulate basal blood flow in the renal cortex or medulla, despite the observation that a considerable portion of NO in the renal interstitial space appears to be produced by NOS1.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: M
authors.initials: M
authors.lastname: Kakoki
authors.forename: A P
authors.initials: AP
authors.lastname: Zou
authors.forename: D L
authors.initials: DL
authors.lastname: Mattson
mesh_terms: D000758:Anesthesia; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007672:Kidney Cortex / Q000098:blood supply / Q000201:enzymology; D007679:Kidney Medulla / Q000098:blood supply / Q000201:enzymology; D017078:Laser-Doppler Flowmetry; D008297:Male; D017551:Microdialysis; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D012965:Sodium Chloride; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D019331:NG-Nitroarginine Methyl Ester