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H. Oku, Y. Kanmara, J. Matsuo, T. Kobayashi, T. Sugiyama, T. Ikeda; Involvement of NADPH Oxidase and Protein Kinase C in Endothelin-1 Induced Superoxide Production in Retinal Microvessels. Invest. Ophthalmol. Vis. Sci. 2009;50(13):413.
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To determine whether endothelin-1 (ET-1) alters the intracellular redox state of retinal microvessels.
Freshly isolated retinal microvessels of rats were exposed to ET-1 (100 nM), and semi-quantitative measurements of the changes in the level of intracellular superoxide. The changes in the ethidium fluorescence of retinal pericytes were recorded by time-lapse photography. The roles played by BQ-123 and BQ-788, receptor antagonists for ETA and ETB receptors respectively, on the changes induced by ET-1was determined. In addition, the effects of apocynin (10 µM), myr-PKC (1.0 µM), allopurinol (100 µM), rotenone (10 µM) and L-NAME (100 µM) on the changes induced by ET-1 were evaluated. The effect of phorbol 12-myristate 13-acetate (PMA, 10 nM), a protein kinase C (PKC) activator, on the microvessels was also determined.
The ethidium fluorescence-positive regions of the blood vessels coincided with the location of retinal pericytes. The intracellular superoxide levels were significantly increased after the addition of ET-1 to the medium, and this elevation was suppressed by apocynin and myr-PKC. Other enzyme inhibitors did not change the level significantly. The ET-1-induced increase of superoxide was significantly suppressed when BQ-123 (1.0 µM) and BQ-788 (1.0 µM) were simultaneously added. PMA (10 nM) mimicked the effect of ET-1.
ET-1 increases the production of superoxide in the retinal microvessel cells by activating NADPH oxidase, and an activation of PKC may be involved in the mechanism. Thus, ET-1 probably augments its vasoconstrictive effects through the formation of superoxides and the decrease in the bioavailability of nitric oxide.
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