The effect of experimentally induced diabetes mellitus on the lipid order and composition of rat cerebral microvessels.

To determine whether diabetes mellitus alters the lipid order and composition of cerebral microvessels, streptozotocin-induced diabetic rats were studied after 5 weeks of chronic hyperglycemia. Diabetes did not affect membrane order or the thermotropic transition temperature of cerebral microvessels as determined from the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH). The cholesterol, phospholipid and fatty acid composition of isolated cerebral microvessels was also not significantly affected in diabetic rats. On the other hand, the cerebral microvessels of diabetic rats had significantly increased concentration of lipid peroxidation byproducts, namely conjugated dienes (the calculated O.D./mg phospholipids was 6.98 +/- 0.52 in controls and 11.82 +/- 0.40 in diabetic rats (P < 0.01). The accumulation of conjugated dienes in cerebral microvessels of diabetic rats in the absence of an alteration in the availability of substrates for peroxidation is consistent with the hypothesis that diabetes mellitus is a disease state which is associated with increased free radical activity. Increased oxidative damage may contribute to the changes in the blood-brain barrier observed in animal models of diabetes.