Uremic levels of BUN do not cause nitric oxide deficiency in rats with normal renal function.
In vitro, 7 days of high blood urea nitrogen (BUN) inhibits endothelial L-arginine transport and nitric oxide synthase (NOS) activity. The present study investigates whether 7 days of high BUN in vivo influences renal hemodynamics, blood pressure (BP), and/or the nitric oxide (NO) system. Normal rats were fed low-nitrate food containing 30% urea for 7 days, which increased BUN (15 +/- 1 to 69 +/- 4 mg/100 ml, P < 0.001). High BUN did not reduce 24-hour urinary nitrite/nitrate excretion (a measure of total NO production). Baseline BP and renal hemodynamics were unaffected by high BUN as were the pressor and renal vasoconstrictor responses to acute NOS inhibition with N(G)-nitro-L-arginine-methyl ester. In addition, high BUN had no impact on renal cortical L-arginine concentration, density of either endothelial NOS or neuronal NOS protein, or renal cortical NOS activity. NOS activity in the brain cerebellum was also unaffected. In conclusion, high BUN did not lead to vasoconstriction or NO deficiency in rats with normal renal function. Further studies are needed to evaluate the effect of high BUN on the NO system in rats with progressive renal functional insufficiency.
Xiao
S
S
Department of Physiology, West Virginia University, Morgantown, West Virginia 26506, USA.
Erdely
A
A
Wagner
L
L
Baylis
C
C
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001806:Blood Urea Nitrogen; D003243:Consciousness; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005919:Glomerular Filtration Rate / Q000502:physiology; D007668:Kidney / Q000098:blood supply / Q000201:enzymology / Q000502:physiology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000172:deficiency*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000502:physiology; D014508:Urea / Q000494:pharmacology; D014511:Uremia / Q000097:blood* / Q000139:chemically induced; D014655:Vascular Resistance / Q000502:physiology
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D014508:Urea; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester