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J. C. Lau, R. A. Linsenmeier; Oxygen Consumption and Distribution in the Diabetic Rat Retina. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5644.
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To investigate the oxygen consumption and distribution in the rat retina as diabetes progresses.
Diabetes was induced in Long-Evans rats with a single intraperitoneal (IP) injection of streptozotocin (65mg/kg) in sodium citrate buffer. Rats with blood glucose >300mg/dl were deemed diabetic and were not treated with insulin. Age-matched controls received a single IP injection of sodium citrate buffer only. At approximately 4 and 12 weeks after induction of diabetes, rats were anesthetized with isoflurane/urethane. PO2 depth profiles were recorded from the retina in vivo using double-barreled oxygen/voltage microelectrodes. Arterial blood parameters were monitored and kept within normal limits. Profiles were obtained in dark-adaptation. The electroretinogram (ERG) was used to assess the position of the electrode in the retina as well as the retina’s condition. Profiles were fitted using the three layer one-dimensional diffusion model to determine photoreceptor oxygen consumption per unit volume, Qav.
After 4 weeks, diabetic rats (n=6) had comparable choroidal PO2, Qav, and average inner retinal PO2 to control rats (n=5). The 12 week diabetic rats (n=5) showed no significant change in choroidal PO2 or Qav compared to age-matched controls (n=5). However, at 12 weeks, the average inner retinal PO2 was significantly lower in controls than in diabetic rats.
Diabetic retinopathy alters the inner retinal vasculature as well as retinal neurons, but its impact on the retinal microenvironment as the disease develops has not been characterized. These experiments are the first to measure intraretinal PO2 profiles in diabetic rats. These measurements show that changes in inner retinal oxygenation are evident after 12 weeks of diabetes, but are opposite to what might have been predicted. PO2 reflects a balance between oxygen supply and consumption, both of which may change in diabetes.
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