R. Salceda et al., CHANGES IN THE REDOX STATE IN THE RETINA AND BRAIN DURING THE ONSET OF DIABETES IN RATS, Neurochemical research, 23(6), 1998, pp. 893-897
Diabetic retinopathy is thought to result from chronic changes in the
metabolic pathways of the retina. Hyperglycemia leads to increased int
racellular glucose concentrations, alterations in glucose degradation
and an increase in lactate/pyruvate ratio. We measured lactate content
in retina and other ocular and non-ocular tissues from normal and dia
betic rats in the early stages of strepto-zotocin-induced diabetes. Th
e intracellular redox state was calculated from the cytoplasmic [lacta
te]/[pyruvate] ratio. Elevated lactate concentration were found in ret
ina and cerebral cortex from diabetic rats. These concentrations led t
o a significant and progressive decrease in the NAD(+)/NADH ratio, sug
gesting that altered glucose metabolism is an initial step of retinopa
thy. It is thus possible that tissues such as cerebral cortex have mec
hanisms that prevent the damaging effect of lactate produced by hyperg
lycemia and/or alterations of the intracellular redox state.