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Purpose: To determine the neuroprotective effect of agmatine (Agm) on the retinas of guinea pigs subjected to a transient ischemia-reperfusion insult., Methods: Twenty-eight guinea pigs were randomly divided into four groups. Forty-five minutes before ischemic insult, the guinea pigs were intraperitoneally administered either Agm (50 mg/kg) (Agm 1) or saline (control 1 group) once, or twice separated by a 12-h interval (Agm 2; control 2). Transient ocular ischemia was achieved under general anesthesia by cannulating an anterior chamber maintainer connected to an infusion line of a semiflexible bottle. The saline reservoir pressure was increased by using a blood pressure tolls cuff to achieve an intraocular pressure (IOP) of 150 mmHg. This IOP was maintained for 90 min. Reperfusion was achieved by pulling off the anterior chamber maintainer. The animals in the Agm 1 and control 1 groups were killed at the end of the 4-h reperfusion period. The eyes were enucleated for histopathological (retinal thickness) and biochemical (thiobarbituric acid reactive substance, TBARS, and nitric oxide, NO) investigation. The animals in the Agm 2 and control 2 groups were killed at the end of a 24-h reperfusion period., Results: The mean retinal thickness of the animals in the Agm 1 (25.94 +/- 1.23 microm) and Agm 2 (24.49 +/- 0.88 microm) groups was lower than that of those in the control 1 (37.60 +/- 2.27 microm) and control 2 (36. 64 +/- 1.32 microm) groups (P < 0.05). The mean TBARS level of the animals in the Agm 1 (8.37 +/- 0.94 nmol/ml) and Agm 2 (8.01 +/- 0.97 nmol/ml) groups was lower than that of those in the control 1 (12.09 +/- 1.27 nmol/ml) and control 2 (12.09 +/- 1.27 and 11.72 +/- 1.63 nmol/ml) groups (P < 0.05). The mean NO level of the animals in the Agm 1 (100.77 +/- 6.20 nmol/ml) and Agm 2 (94.63 +/- 5.24 nmol/ml) was lower than that of those in the control 1 (131.77 +/- 4.61 nmol/ml) and control 2 (122.43 +/- 4.35 nmol/ml) groups (P < 0.05). There were positive correlations between the TBARS and NO levels and retinal thickness in the Agm and control groups., Conclusion: Agmatine exerts a significant neuroprotective effect on guinea pig retinas after transient ischemia-reperfusion insult.

Purpose: To investigate the relationship between the erythrocyte membrane fatty acid components and diabetic retinopathy in patients with type 2 diabetes mellitus., Methods: The study was performed in 40 patients. Thirty of the 40 were type 2 diabetic patients classified into three groups according to Early Treatment Diabetic Retinopathy Study Group (ETDRS) criteria: 10 with mild-moderate nonproliferative retinopathy (group 1), 10 with moderate-severe nonproliferative retinopathy (group 2), and 10 with proliferative retinopathy (group 3). Ten age- and sex-matched healthy nondiabetic individuals were selected as controls. We examined the fatty acid composition of the erythrocyte membrane by a gas chromatographic method., Results: In patients with nonproliferative diabetic retinopathy, we found statistically significant decreases in palmitic and stearic acids, and statistically significant increases in oleic, linoleic, behenic, and lignoceric acids, while arachidic and arachidonic acids remained unchanged. Except for the increase in arachidic acid, the results were similar to those in the proliferative retinopathy patients., Conclusions: The fatty acid component of the erythrocyte membrane alters in type 2 diabetes mellitus. Prospective studies are needed to evaluate the relationship between the free-fatty acid composition of erythrocytes and diabetic retinopathy.