Intravenous administration of L-arginine increases retinal and choroidal blood flow

Am J Ophthalmol. 2005 Jul;140(1):69-76. doi: 10.1016/j.ajo.2005.02.016.


Purpose: Nitric oxide (NO) is among the most important regulators of ocular perfusion. L-arginine, an amino acid, is the precursor of NO synthesis. The aim of the present study was to determine whether administration of L-arginine affects ocular blood flow.

Design: L-arginine (1 g/min) or placebo was administered intravenously for 30 minutes in 12 healthy volunteers in a randomized, double-masked, two-way cross-over design.

Methods: Ocular hemodynamics were measured before, in the last 10 minutes of the infusion period, as well as 30 minutes after cessation of the administration. Retinal vessel diameters were measured with a retinal vessel analyzer, red blood cell velocities with bidirectional laser Doppler velocimetry, and pulsatile choroidal blood flow was measured using laser interferometry.

Results: L-arginine significantly decreased mean arterial pressure by -8 +/- 5% and -6 +/- 7% at the two time points (P < .01), respectively. Intravenous administration of L-arginine increased choroidal blood flow by +10 +/- 6% and +12 +/- 7%, respectively. Retinal venous diameters decreased by -2.5 +/- 2.1% and -1.4 +/- 2.7%, respectively, whereas red blood cell velocity significantly increased after administration of L-arginine by +22 +/- 23% and +20 +/- 19% at the two time points. Thus, calculated blood flow in retinal veins, increased by +21 +/- 18% and +21 +/- 19% before and after the end of L-arginine infusion.

Conclusions: Intravenous administration of L-arginine increases retinal and choroidal blood flow in healthy volunteers. Whether this effect is related to an increased NO-production or an unidentified mechanism remains to be clarified. However, administration of L-arginine might be an interesting new approach to therapeutically increase ocular blood flow in ocular vascular disease.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Arginine / administration & dosage*
  • Blood Flow Velocity / drug effects
  • Blood Pressure
  • Choroid / blood supply*
  • Cross-Over Studies
  • Double-Blind Method
  • Humans
  • Infusions, Intravenous
  • Interferometry
  • Intraocular Pressure
  • Laser-Doppler Flowmetry
  • Lasers
  • Male
  • Photic Stimulation
  • Regional Blood Flow
  • Retinal Vessels / physiology*
  • Vasodilation


  • Arginine