Insulin-induced nitric oxide production and high glucose in microvessels of rat retina

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Insulin-induced nitric oxide (NO) production in retinal microvessels was evaluated. The retinal microvessels were incubated in different concentration of glucose with or without addition of insulin. Changes of NO production in the retinal microvessels were semiquantitatively determined by the time-lapse recording offluorescent intensity of DAF using a laser scanning confocal microscope. In addition, cell viability of pericyte in each condition was assayed by trypan blue exclusion. Exposure of microvessels to insulin in 5.5 mM glucose, the fluorescent intensity was significantly increased, while the insulin-induced NO production was significantly suppressed when vessels were incubated in 20 mM glucose. Insulin increased production of NO and may contribute to the microcirculation of retina. However, this NO-mediated action of insulin is suppressed under high glucose condition. These results may account for impairment of retinal circulation under diabetic conditions.