Fig. 1. Vascular histopathology characteristic of the retinopathy that develops in diabetic dogs (5 years diabetes). Lesions visible include a saccular capillary microaneurysm (MA), degenerate and acellular capillaries (AC), and pericyte ghosts (PG).

found to be less effective (17), similar to findings in diabetic patients (18). Administration of aminoguanidine from the onset of diabetes (also for 5 years) significantly inhibited the development of retinal microaneurysms, acellular capillaries, and pericyte ghosts in diabetic dogs, and administration of moderate doses of aspirin for an equal duration significantly inhibited the development of retinal hemorrhages and acellular capillaries over the 5 years of study (19). Diabetic dogs treated with the nonsteroidal antiinflammatory drug, Sulindac, had less retinal capillary basement membrane volume than did untreated diabetic dogs (20). Administration of an aldose reductase inhibitor in doses sufficient to totally prevent the diabetes-induced accumulation of sorbitol had no effect on the development of retinal histopathology in diabetic dogs (12).

Advantages and Disadvantages of the Model

The retinal histopathology that develops in this animal model is very similar to that which develops in diabetic patients, and the severity of the retinopathy can become more severe than develops in shorter-lived models such as rodents. Nonetheless, preretinal neovascularization has not been observed to develop in the 5–8 years of diabetes that this model has been studied. In addition, the cost, slow development of lesions, and lack of availability of antibodies or molecular biology reagents have made dog models less popular as models for the study of diabetic complications in recent years.

DIABETIC CATS

Type of Diabetes

Studies of diabetic cats to date have focused on type 1 diabetes, the diabetes being induced by pancreatectomy with or without alloxan (21). One cat with long-standing spontaneous diabetes also was studied.