Vasomotor Effect of Intravitreal Juxta-arteriolar Injection ofl-Lactate on the Retinal Arterioles after Acute Branch Retinal Vein Occlusion in Minipigs

Abstract

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