Intravenous Administration of L-Arginine Increases Retinal and Choroidal Blood Flow

Garhöfer, Gerhard; Resch, Hemma; Lung, Solveig; Weigert, Günther; Schmetterer, Leopold

doi:10.1016/j.ajo.2005.02.016

« Previous Next »American Journal of Ophthalmology
Volume 140, Issue 1 , Pages 69.e1-69.e9, July 2005

Intravenous Administration of L-Arginine Increases Retinal and Choroidal Blood Flow

Gerhard Garhöfer, MD
- Department of Clinical Pharmacology, University of Vienna, Vienna, Austria.
- Department of Ophthalmology, University of Vienna, Vienna, Austria.
Hemma Resch, MD
- Department of Clinical Pharmacology, University of Vienna, Vienna, Austria.
Solveig Lung, MD
- Department of Clinical Pharmacology, University of Vienna, Vienna, Austria.
Günther Weigert, MD
- Department of Clinical Pharmacology, University of Vienna, Vienna, Austria.
Leopold Schmetterer, PhD
- Department of Clinical Pharmacology, University of Vienna, Vienna, Austria.
- Institute of Medical Physics, University of Vienna, Vienna, Austria.
- Inquiries to Leopold Schmetterer, PhD, Department of Clinical Pharmacology, Währinger Gürtel 18-20, A-1090 Vienna, Austria; fax ++43-1-40400-2998

Accepted 1 February 2005. published online 13 June 2005.

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.