Vasomotor effect of intravitreal juxta-arteriolar injection of L-lactate on the retinal arterioles after acute branch retinal vein occlusion in minipigs.

Purpose: To investigate the effect of L-lactate on retinal arteriolar diameter after acute branch retinal vein occlusion (BRVO) in minipigs.

Methods: Thirteen eyes of 13 minipigs were evaluated, with the animals under general anesthesia. BRVO was induced by a standard method of argon laser endophotocoagulation. Two hours after BRVO, an intravitreal, juxta-arteriolar microinjection of 50 μL L-lactate 0.5 M (pH 7.4) was performed in nine eyes. Four eyes received a microinjection of 50 μL of the solvent (pH 7.4) that was used to prepare the solution of L-lactate and served as controls. Retinal arteriolar diameter changes were measured using a retinal vessel analyzer.

Results: Overall (n = 13), 2 hours after BRVO, there was a 9.0% ± 1.4% decrease in the retinal arteriolar diameter in the affected ares compared to baseline (P < 0.001). An increase of 26.2% ± 8.2% (P = 0.004) of the arteriolar diameter was evidenced 5 minutes after L-lactate juxta-arteriolar microinjection (n = 9) compared with the diameter before L-lactate microinjection. Thereafter, the vasodilatory effect of L-lactate persisted and remained significant until the end of the study period (27.7% ± 7.8% at 30 minutes) compared with the diameter before L-lactate microinjection (P = 0.002). Microinjection of the solvent alone (n = 4) did not produce any significant effect on the retinal arterioles, which remained constricted at all time-points (P > 0.1).

Conclusions: These findings demonstrate a significant arteriolar vasodilation after intravitreal juxta-arteriolar L-lactate microinjection in eyes with experimental BRVO in the affected areas. L-lactate microinjection can reverse the arteriolar vasoconstriction that occurs in acute experimental BRVO.