Ocular blood flow and retinal metabolism in Abyssinian cats with hereditary retinal degeneration

PURPOSE. To investigate if retinal blood flow decreases with progression of the disease in Abyssinian cats with progressive retinal atrophy (PRA), to examine if the choroidal blood flow was affected by the disease, and to det ermine the uptake of glucose and formation of lactate in the outer retina. METHODS. Local blood flow in different parts of the eye was determined with radioactive microspheres, in 9 normal cats and in 10 cats at different sta ges of PRA. Three blood flow determinations were made in each animal, durin g control conditions, after TV administration of indomethacin and after sub sequent administration of N-omega-nitro-L-arginine (L-NA). Blood samples f rom a choroidal vein and a femoral artery were collected to determine the r etinal formation of lactate and uptake of glucose. RESULTS. In Abyssinian cats with PRA (n = 10), the retinal blood flow was s ignificantly (P less than or equal to 0.01) lower than in normal cats (n = C)) during control conditions, 6.4 +/- 1.7 compared with 14.1 +/- 1.9 g min (-1) (100 g)(-1). The vascular resistance in the iris and ciliary body was significantly higher in the cats at a late stage of PRA, both compared with normal cats and to cats at an early stage of the disease, whereas the chor oidal vascular resistance was not significantly affected. Indomethacin had no effect on ocular blood flows in normal cats, bur in cats with PRA, irida l blood flow was more than doubled after indomethacin. The retinal formatio n of lactate was significantly (P less than or equal to 0.001) lower in cat s with PRA than in normal cats. 0.111 +/- 0.035 (n = 8) compared with 0.318 +/- 0.024 (n = 8) mu mol min L. The uptake of glucose was not significantl y different in cats with PRA. CONCLUSIONS. Retinal blood flow is severely decreased in Abyssinian cats at a late stage of retinal degeneration, whereas the choroidal microcirculati on is not significantly affected by the disease. At a late stage of retinal degeneration, vascular resistance in the iris is significantly increased, which at least in part could be caused by cyxlooxygenase products.