Exogenous L-arginine does not affect angiotensin II-induced renal vasoconstriction in man.
OBJECTIVE
It has been suggested that provision of the substrate of nitric oxide (NO) synthesis, L-arginine, might influence the effects of renal vasoconstrictors. We have therefore studied the effects of pretreatment or concomitant administration of L-arginine on angiotensin II (ANG II)-increased renovascular resistance.


METHODS
The study was conducted in a double-blind, randomized, cross-over design. Eight healthy subjects were assigned to placebo or a continuous intravenous coinfusion of ANG II (5.0 ng kg[-1] min[-1], infusion period 75 min) with L-arginine (17 mg kg[-1] min[-1], infusion period 30 min). Nine further subjects received a continuous infusion of ANG II with or without pretreatment of L-arginine. Changes in renal plasma flow (RPF) were estimated by the steady state clearance of PAH.


RESULTS
L-arginine alone increased RPF to 110 +/- 10% over baseline (P < 0.003). The ANG II-induced decrease in RPF was not affected by pretreatment or coinfusion of L-arginine.


CONCLUSIONS
Our results demonstrate that a counterregulatory response of the renal vasculature to high levels of ANG II does not depend on exogenous L-arginine. In healthy subjects, this lack of functional antagonism at the renal vasculature is therefore not a result of NO substrate availability.
Wolzt
M
M
Department of Clinical Pharmacology, Vienna University, Austria.
Ugurluoglu
A
A
Schmetterer
L
L
Dorner
G
G
Zanaschka
G
G
Mensik
C
C
Eichler
H G
HG
D000328:Adult; D000804:Angiotensin II / Q000494:pharmacology*; D001120:Arginine / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004347:Drug Interactions; D006801:Humans; D007262:Infusions, Intravenous; D007668:Kidney / Q000098:blood supply*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology; D010919:Placebos; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D010919:Placebos; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D009569:Nitric Oxide; D001120:Arginine