Enhanced Production of Nitric Oxide Leads to ATP Collapse in the Retinas of Otsuka Long-Evans Tokushima Fatty Rats, a Model of Human Diabetes.

Purpose: We determined nitric oxide (NO) production via inducible NO synthase (iNOS) by hyperglycemia using the retina of Otsuka Long-Evans Tokushima Fatty rats (OLETF rats), and investigated the relationship between ATP contents and NO production in the retinas of OLETF rats.

Methods: Long-Evans Tokushima Otsuka rats (LETO rats, normal rats) and OLETF rats (model rat for diabetes mellitus) aged 60 weeks of age were used. Plasma glucose (Glu) levels were determined using an Accutrend GCT System, and NO levels were measured by the microdialysis method as nitrite ([Formula: see text]). Cytochrome c oxidase (CCO) activity was measured using a Mitochondrial Isolation Kit and Cytochrome c Oxidase Assay Kit, and ATP levels were determined using a Sigma ATP Bioluminescent Assay Kit and a luminometer AB-2200.

Results: [Formula: see text] levels in the retinas of OLETF rats were significantly higher than in LETO rats, and the [Formula: see text] levels in the retinas of 60-week-old OLETF rats increased with increasing Glu. CCO activity in the retinas of OLETF rats showed no significant difference from that in LETO rats; however, ATP levels in the retinas of OLETF rats were significantly lower than those in LETO rats. The oral administration of aminoguanidine or disulfiram, an iNOS inhibitor, attenuated the decrease in ATP levels in the retinas of 60-week-old OELTF rats.

Conclusion: The present study demonstrates that NO production via iNOS in the retinas of 60-week-old OLETF rats is caused by hyperglycemia, and that NO causes a decrease in ATP contents in the retinas of 60-week-old OELTF rats. It is possible that the low ATP contents caused by NO may affect the normal functioning of the retina in OLETF rats.