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L. Wagenfeld, F. von Domarus, M. Klemm, P. Galambos, N. Matthiesen, G. Richard, O. Zeitz; Regulation of Vascular Tone in the Ophthalmic Artery: Impact of Hydroxyl Radicals. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4133.
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Oxygen free radicals are involved in the pathogenesis of several ocular and cardiovascular diseases. Radicals may disrupt the regulation of vascular tone and thereby lead to the generation of more oxidative stress. Aim of the presents study is to investigate the influence of hydroxyl radicals on the regulation of myogenic tone of the ophthalmic artery.
Rat ophthalmic arteries were freshly dissected and kept in a cold physiologic salt solution (PSS). The isolated arteries were placed in a perfusion setup and were pressurized in steps of 10 mmHg up to 180 mmHg. At each pressure step the diameter of the vessel was recorded by a digital edge-detection system. The diameter-pressure relation was recorded three times with each preparation, twice with 1.8mM Ca2+ and finally under Ca2+-free conditions after adding EDTA to the PSS buffer. This last cycle served to obtain the passive diameter-pressure relation. The myogenic tone was calculated as follows: Dp - Da / Dp x 100. (Dp=passive diameter, Da =active diameter in presence of Ca2+). Between the first and second cycle, the preparation was exposed for 10s to hydroxyl radicals generated from H2O2 and Fe3+ (FeNTA). For the control experiments a sham radical exposure was done. Arterial outer diameter was measured during the whole procedure. Outer diameters before and after radical exposure, or between both pressurizations in the control group were compared using an ANOVA.
Mean arterial diameters were measured between 240 µm for arteries pressurized with 10 mmHg and up to 332 µm for arteries passively dilated with 180 mmHg. In accordance to previously published data, our experiments show a stable and reproducible myogenic tone between 70 and 180 mmHg (myogenic tone between 8.6 +/- 2.3% and 13.6 +/- 3.1%, n=5). While in the control experiments the diameter-pressure relation is identically in the first and second cycle of the experiment, it is significantly altered after radical exposure (p<0.01, n=7).
An OFR exposure can alter the myogenic response of blood vessels and could therefore provoke a disturbance in ocular blood flow regulation.
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