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Simon M. Pedersen, Toke Bek; The Diameter Response To L-lactate And The Prostaglandin Analogue U46619 Is Different In Porcine Retinal Arterioles And Capillaries In Vitro. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6825.
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Disturbances in the regulation of retinal blood flow are involved in the pathogenesis of vision threatening diseases such as diabetic retinopathy. These flow disturbances are due to changes in the tone regulation of retinal arterioles, but recent evidence suggests that disturbances in the regulation of retinal microcirculation, such as lactate induced vasodilatation during retinal ischemia, are also involved in the disease pathogenesis. Therefore, it is necessary to introduce in vitro methods for studying the retinal microcirculation.
A special tissue chamber was developed for perfusion of a porcine hemiretina while controlling flow, oxygenation, pH, and ambient metabolite concentrations. The diameter of retinal capillaries were quantified by monochrome microscopy video recordings during intraluminal perfusion with a fluorescent dextran solution. The linear flow was quantified by counting the passage per time unit of fluorescence labelled erythrocytes. In preliminary experiments changes in the diameter of small retinal vessels were measured during intraluminal perfusion with L-lactate and with the prostaglandin analogue U46619.
Intraluminal perfusion with L-lactate had a significant dilating effect on retinal arterioles from (mean±SEM, n=4) 48.5±9.6μm to 63.1±9.6μm (p=0.01), and a significant contractile effect on retinal capillaries from 7.9±0.6μm to 6.4±0.5 μm (p=0.0004), whereas U46619 had a significant contracting effect on arterioles from 69.4±8.5μm to 48.5±9.6 μm (p=0.01), but no effect on the diameter of retinal capillaries from 7.9±0.6μm to 7.0±0.4μm (p=0.32).
L-lactate and U46619 have different effects on the diameter of arterioles and capillaries in the porcine retina in vitro. This emphasizes that the mechanisms underlying flow regulation in retinal arterioles differs from the regulation of retinal microcirculation. This may have implications for the development of new treatments to normalize blood flow in retinal disease.
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