Retinal angiotensin II and angiotensin-(1-7) response to hyperglycemia and an intervention with captopril

Figure 1.. Confocal images of localization of Ang II and nuclei merge in retina sections at 3, 9, and 15 weeks after diabetes was induced: (a–c) nondiabetic and (d–f) diabetic rats. In the nondiabetic rats, Ang II antiserum labeled Müller cells. Ang II extended from the footplates of the Müller cell (arrowhead) through cell processes in the IPL into the INL. Immunoreactivity was marked in the Müller cell endfeet and extended into the cellular processes. In the diabetic retina, Ang II extended through the entire retina from the Müller cell footplates (arrowhead), cell processes in the IPL through the INL and OPL into the ONL (short and long arrow). The higher intensity and increase in extent of labeling in Müller cell processes was clear at three weeks after diabetes was induced. This pattern of labeling was maintained throughout the 15 weeks of diabetes. GCL: ganglion cell layer; IPL and OPL: inner and outer plexiform layers; INL and ONL: inner and outer nuclear layers. Scale bar = 50 µm.

Figure 2.. Confocal images of localization of Ang-(1-7) in retinal sections. Confocal images of Ang-(I-7) and nuclei merge in retina at 3, 9, and 15 weeks after diabetes was induced: (a–c) nondiabetic and (d–f) diabetic rats. Ang (1-7) antiserum-labeled Müller cells (arrowhead). In the nondiabetic retina, Ang-(I-7) extended from the footplates of the Müller cell (short arrow) through cell processes extending up to the photoreceptor layer (long arrow). In diabetic rats, the intensity and extent of labeling decreased steadily with the duration of hyperglycemia. Scale bar = 50 µm.

Figure 3.. Quantitative evaluation of Ang II (a) and Ang-(1-7) (b) in nondiabetic and diabetic retinas at 3, 9, and 15 weeks after induction of diabetes. Values are mean ± SEM. Within group: Ang II and Ang (1-7) showed differences among the three time points only in the nondiabetic retinas (p = 0.028 and p = 0.003, respectively). Mean levels of Ang II in the diabetic group were statistically significantly higher than those in the nondiabetic group (**p < 0.001). Mean levels of Ang-(1-7) in the diabetic group were statistically significantly lower than those in the nondiabetic group (**p < 0.001). Nondiabetic retina (black square); diabetic retina (gray square).

Figure 4.. Confocal images of localization of Ang II and Ang-(I-7) and nuclei merge in retina from (a and d) control nondiabetic rats, (b and e) diabetic rats, and (c and f) diabetic rats treated with captopril. Ang II and Ang-(1-7) were localized in Müller cells (arrowhead) of nondiabetic, diabetic, and captopril-treated rats as well. Ang II was localized to the Müller cell footplates and the Müller cell processes (short and long arrows). In diabetic rats (b), the intensity of labeling was higher than in the nondiabetic controls (a); while ACEI captopril decreased the level of Ang II staining compared with diabetic, it was no different than the level of staining of Ang II (c) compared with controls. In the nondiabetic retina, Ang-(I-7) extended from the footplates of the Müller cell (arrowhead) through cell processes extending up to the photoreceptor layer (d, long arrow). The extent and intensity of Ang-(1-7) labeling was significantly reduced in the diabetic retina (e). Treatment of diabetic rats with ACEI restored the intensity and extent of Ang-(1-7) labeling toward levels found in control nondiabetic animals (f). Scale bar = 50 µm.

Figure 5.. Quantitative evaluation of Ang II and Ang-(1-7) in nondiabetic, diabetic, and captopril-treated diabetic rat retinas at 12 weeks after induction of diabetes. Values are mean ± SEM. *p < 0.05, **p < 0.01 as indicated. Both outcomes showed statistical differences among the three groups.