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Abstract
Purpose
To compare retinal ultrastructures of diabetic rats (OLETF, Otsuka Long-Evans Tokushima Fatty) with those of age-matched non-diabetic rats (LETO, Long-Evans Tokushima Otsuka) using transmission electron micrography (TEM).
Methods
The body weights and blood sugar levels of the OLETF rats and LETO rats (n=5) were measured at 10 and 50 weeks of age. Using a TEM, we compared the ultrastructural changes between the retinas of the 50-week-old OLETF and LETO rats. We analyzed the sizes of the pericytes and the thicknesses of the retinal capillary basement membranes between the two groups. Comparisons were made using a Scion Image®.
Results
The mean body weight and blood sugar levels of the 50-week-old OLETF rats were significantly higher than those of the LETO rats (p<0.05). The thicknesses of the retinal capillary basement membranes in the outer plexiform layer and the size of pericytes were significantly increased in the OLETF rats at 50 weeks of age (p<0.05). The number of nuclei in the inner nuclear layer and the outer nuclear layer (photoreceptor cell nuclei) significantly decreased (p<0.05). However, the height of the RPE cells and basal infoldings showed no significant differences between the OLETF and LETO rats.
Conclusions
The retinal changes in the OLETF rats were observed relatively early at 50 weeks of age. These changes are similar to those seen in human diabetic retinopathy. Change in the capillaries is one feature of early retinal change. OLETF rats may be a useful animal model in NIDDM to examine diabetic retinal changes.
References
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Figure 1.
Electron micrographs of the outer plexiform layer of a 50-weeks-old LETO (A) and OLETF rat (B). The basement membrane of the retinal capillary of the OLETF rat is thickened and the capillary lumen is narrow, tortous and irregular. The cytoplasm of endothelial cells and pericytes of the OLETF rat are degenerated with increased vesicles and vacuoles in the cytoplasm, and vacuolated mitochondria. Bar=1 μm (original magnification, A&B: × 8000)
Figure 2.
Electron micrographs of the inner nuclear layer of a 50-weeks-old LETO (A) and OLETF rat (B). A decrease in the cell density, degenerated cells and cell nuclei are observed in the inner nuclear layer of the OLETF rat. Bar=2 μm (original magnification, A&B: ×6000)
Figure 3.
Electron micrographs of the outer nuclear layer of a 50-weeks-old LETO (A) and OLETF rat (B). A decrease in the cell density of the OLETF rat is observed. Bar=2 μm (original magnification, A&B: ×6000)
Figure 4.
Electron micrographs of the retinal pigment epithelium containing the basal infoldings of a 50-weeks-old LETO (A) and OLETF rat (B). With a decrease in the height of RPE cells, basal infoldings (arrows) are poorly developed in the OLETF rat. Bar=2 μm (original magnification, A&B: ×6000)
Table 1.
| | OLETF* (n‡=5) | LETO† (n‡=5) | p-value |
|---|---|---|---|
| 10 weeks | | | |
| Body weight (g) | 393.0±33.9 | 328.5±23.3 | 0.25 |
| Blood glucose (mg/dl) | 223.8±26.4 | 177.4±30.1 | 0.31 |
| 50 weeks | | | |
| Body weight (g) | 783.5±35.2 | 622.0±23.7 | <0.05 |
| Blood glucose (mg/dl) | 215.2±20.2 | 138.0±10.2 | <0.05 |
Table 2.
| 50-weeks-old rats | OLETF* (n‡=20) | LETO† (n‡=20) | p-value |
|---|---|---|---|
| The size of pericytes (μm2) | 5.53±3.31 | 1.99±2.21 | <0.05 |
| Retinal capillary BM§ thickness (nm) | 144.2±9.7 | 122.4±10.2 | <0.001 |
| Nuclei in INL∏ (number) | 8.5±0.40 | 12.5±0.56 | <0.01 |
| Nuclei in ONL＃ (number) | 36.5±0.64 | 42.0±0.55 | <0.01 |
| Height of RPE** Cells (μm) | 4.592±0.031 | 5.121±0.056 | 0.16 |
| Height of basal infoldings (μm) | 0.527±0.035 | 0.884±0.021 | 0.11 |
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