The effect of reactive oxygen species on the myogenic tone of rat ophthalmic arteries with and without endothelium

BACKGROUND: Reactive oxygen species (ROS) play an important role in the pathogenesis of various ocular diseases. ROS can induce vasodilation or vasoconstriction depending on the species, the tested vessel bed, and the condition of the vessel. This study investigates the effect of different dosages of ROS on the tone of rat ophthalmic arteries.

METHODS: Freshly dissected rat ophthalmic arteries were pressurized in a perfusion setup in steps of 10 mmHg to 180 mmHg in three consecutive cycles. The first cycle was run under mostly physiological conditions, the second cycle was run after ROS treatment, and the third cycle as passive dilation after all Ca(2+) was removed from the solution. ROS-induced dilation or constriction was calculated in relation to the passive dilation. All experiments were performed with or without endothelium.

RESULTS: For vessels with endothelium, dilation in control experiments was 20.0 ± 0.1%; after 5 s of ROS dilation was 74.4 ± 0.6%, and after 20 s 87.4 ± 0.3%. ANOVA revealed significant differences between these groups (P = 0.048). For vessels without endothelium, a slight dilation was seen in control experiments (14.5 ± 0.4%), which was also present after 5 s of ROS treatment (15.4 ± 0.4%). Treatment with ROS for 20 s led to a constriction of the vessel preparations (-16.6 ± 0.5%; P = 0.831).

CONCLUSIONS: ROS led to a vasodilation in vessels with endothelium that was not seen in vessels without endothelium. Endothelial function seems to determine the effect of ROS on the vessel tone in isolated rat ophthalmic arteries.