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Vickie H. Y. Wong, Algis J. Vingrys, Andrew I. Jobling, Bang V. Bui; Susceptibility of Streptozotocin-Induced Diabetic Rat Retinal Function and Ocular Blood Flow to Acute Intraocular Pressure Challenge. Invest. Ophthalmol. Vis. Sci. 2013;54(3):2133-2141. doi: 10.1167/iovs.13-11595.
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© ARVO (1962-2015); The Authors (2016-present)
To consider the hypothesis that streptozotocin (STZ)-induced hyperglycemia renders rat retinal function and ocular blood flow more susceptible to acute IOP challenge.
Retinal function (electroretinogram [ERG]) was measured during acute IOP challenge (10–100 mm Hg, increments of 5 mm Hg, 3 minutes per step, vitreal cannulation) in adult Long-Evans rats (6 weeks old; citrate: n = 6, STZ: n = 10) 4 weeks after citrate buffer or STZ (65 mg/kg, blood glucose >15 mM) injection. At each IOP, dim and bright flash (−4.56, −1.72 log cd.s.m−2) ERG responses were recorded to measure inner retinal and ON-bipolar cell function, respectively. Ocular blood flow (laser Doppler flowmetry; citrate: n = 6, STZ: n = 10) was also measured during acute IOP challenge. Retinas were isolated for quantitative PCR analysis of nitric oxide synthase mRNA expression (endothelial, eNos; inducible, iNos; neuronal, nNos).
STZ-induced diabetes increased the susceptibility of inner retinal (IOP at 50% response, 60.1, CI: 57.0–62.0 mm Hg versus citrate: 67.5, CI: 62.1–72.4 mm Hg) and ON-bipolar cell function (STZ: 60.3, CI: 58.0–62.8 mm Hg versus citrate: 65.1, CI: 61.9–68.6 mm Hg) and ocular blood flow (43.9, CI: 40.8–46.8 versus citrate: 53.4, CI: 50.7–56.1 mm Hg) to IOP challenge. Citrate eyes showed elevated eNos mRNA (+49.7%) after IOP stress, an effect not found in STZ-diabetic eyes (−5.7%, P < 0.03). No difference was observed for iNos or nNos (P > 0.05) following IOP elevation.
STZ-induced diabetes increased functional susceptibility during acute IOP challenge. This functional vulnerability is associated with a reduced capacity for diabetic eyes to upregulate eNos expression and to autoregulate blood flow in response to stress.
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