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H.D. VanGuilder, A.J. Barber, Penn State Retina Research Group; Insulin Partially Normalizes Calcium Homeostasis in Retinal Neurons Cultured With Elevated Glucose . Invest. Ophthalmol. Vis. Sci. 2005;46(13):424.
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Purpose: Intracellular calcium homeostasis is critical to neuronal function. The aim of this study was to test the hypothesis that high glucose increases the intracellular calcium response to stimulation with potassium chloride in cell culture models of retinal neurons, and that the elevated response is partially reversed by insulin. Methods: Three cell culture models of retinal neurons (R28, RGC–5, and primary retinal cultures) were grown in 5mM or 20mM glucose and treated with 10nM insulin. The intracellular calcium response to 20mM KCl was measured by live–cell confocal microscopy with Fluo–4, a cell–permeable fluorescent calcium indicator. Results: 20mM glucose significantly increased the amplitude and duration of the calcium response to KCl, compared to 5 mM glucose. 10nM insulin significantly reduced the amplitude and duration of the calcium–response in cells cultured with 20mM glucose compared to untreated high–glucose controls. Conclusions: Elevated extracellular glucose increases the intracellular calcium response to potassium and delays recovery in culture models of retinal neurons. These data suggest that elevated glucose may pose a threat to retinal function by altering neuronal calcium homeostasis. Furthermore, insulin action may contribute to the regulation of intracellular calcium in retinal neurons.
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