A NOVEL METHOD TO ASSESS REACTIVITIES OF RETINAL MICROCIRCULATION

This study introduces a novel method of bovine retinal microcirculatio n preparation to assess reactivities of retinal microvessels in ex viv o. This preparation is perfused intraluminally through the retinal art ery. Effects of vasoactive hormones on these microvessels can be studi ed by perfusion or topical application to muscle bath. Effects of thes e compounds on the retinal microvessels of 1A (180- to 200-mu m diamet ers), 2A (50- to 60-mu m diameter), and 3A (20- to 30-mu m diameter) c an be assessed simultaneously using video microscopy. In this study, t he water-soluble compound endothelin-l, when applied topically, caused dose-dependent vasoconstriction of all microvessels but had no effect when perfused intraluminally. On the other hand, lipid-soluble prosta glandin F-2 alpha (PGF(2 alpha)) caused dose-dependent vasoconstrictio n when administered either intra- or extraluminally. Furthermore, prec onstricted retinal arterioles (by PGF(alpha)) were dilated in a dose-d ependent manner when acetylcholine was perfused through the retinal ar tery. This vasodilation was attenuated by atropine or N-3-monomethyl a rginine, a nitric oxide synthase inhibitor. Topical potassium chloride also caused dose-dependent vasoconstriction of all retinal microvesse ls. Fluorescein angiography showed no breakdown of the blood-retinal b arrier. Thus, in this ex vivo perfused bovine retinal microcirculation preparation, the water-soluble compounds may not cross the blood-reti nal barrier to affect microcirculation while lipid soluble can affect this circulation. Additionally this study shows that endothelial-deriv ed compounds, endothelin and nitric oxide, caused vasoconstriction and dilation, respectively, (C) 1994 Academic Press,