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Retinal blood flow by hydrogen clearance polarography in the streptozotocin-induced diabetic rat
S J Cringle1, D Y Yu, V A Alder
1Lions Eye Institute, University of Western Australia, Nedlands.
Purpose:
The authors compared retinal blood flow in rats after 5 weeks of streptozotocin (STZ)-induced diabetes with that in age-matched control animals.
Methods:
The flow measurements were based on the hydrogen clearance technique and the intraocular placement microelectrodes at the surface of the retina. The hydrogen was delivered by bolus injection (100 microliters) of hydrogen-saturated saline into the ipsilateral carotid artery using a cannula through the lingual artery. The rats were anesthetized and artificially ventilated. Care was taken to match the systemic blood pressure and blood gases in the two groups.
Results:
The mean retinal blood flow in the STZ group after 5-6 weeks duration of hyperglycemia was 487 +/- 59 ml/min/100g (standard error) compared with 330 +/- 16 ml/min/100 g in the age-matched controls. The variation in retinal blood flow was far more pronounced in the STZ group, even in different locations in the same eye. Changes in fundus appearance were also noted, with second-order arterioles being more apparent and the retina more "pinkish" in appearance in the STZ animals.
Conclusions:
The mean retinal blood flow in the region of retina studied in the two groups was significantly higher in the STZ animals than in age-matched controls. The increased heterogeneity of retinal blood flow may reflect a disruption to the normal blood flow control mechanisms in the retina after only 5 weeks of STZ-induced diabetes.