Intravitreal L‐arginine injection reverses the retinal arteriolar vasoconstriction that occurs after experimental acute branch retinal vein occlusion

Abstract

Abstract Purpose To investigate the effect of L‐Arginine on the retinal arteriolar diameter following acute branch retinal vein occlusion (BRVO) in minipigs. Methods Under general anesthesia, 10 eyes of 10 minipigs were evaluated. Two hours after BRVO, an intravitreal juxta‐arteriolar microinjection of 30 µl L‐Arginine 1 mM (pH=7.4) was performed in 7 eyes. Three eyes received a microinjection of 30 µl of the solvent (pH=7.4) that was used to prepare the solution of L‐Arginine and served as controls. Retinal arteriolar diameter changes were measured using a Retinal Vessel Analyzer. Results Overall (n=10), two hours after BRVO there was a 10.5 ± 1.9 % decrease in the retinal arteriolar diameter in the affected territories compared to baseline (p<0.05). An increase of 16.0 ± 3.0 % (p< 0.01) and 21.0 ± 7.0 % (p<0.05) of the arteriolar diameter was evidenced 10 and 15 minutes respectively after L‐Arginine injection (n = 7) compared to the diameter prior to L‐Arginine injection. Thereafter, the vasodilatory effect of L‐Arginine started to decrease but persisted and remained significant at the end of the study period (5.0 ± 1.5 % at 30 min, p<0.05). Microinjection of the solvent that was used to prepare the solution of L‐Arginine (n=3) did not produce any significant effect on the retinal arterioles, which remained constricted at all time‐points (p>0.1). Conclusion We found a significant vasodilation after intravitreal juxta‐arteriolar L‐Arginine microinjection in eyes with experimental BRVO. L‐Arginine microinjection can be a beneficial therapeutic option in acute BRVO, reversing the arteriolar vasoconstriction by stimulating NO production.