The role of endothelium in vascular response of diabetic rats

The responses of aortas to various vasoactive agents were compared in streptozotocin-induced diabetic male rats and age-matched normal controls. There was a shift of the dose-response curve of norepinephrine (NE) to the right from streptozotocin-induced diabetic rats of 8 weeks duration as compared that of to normal rats. The median effective concentration (EC50) of NE in diabetic aortas to NE was significantly increased from 10(-7.5) M to 10(-7.2) M, while the maximum response of diabetic aortas to NE was not different from that of normal controls. In addition, the EC50 and maximum contractile response to KCl were also not different between the two groups. Meanwhile, the contractions induced by angiotensins I and II, were also significantly attenuated in diabetic aortas. The endothelium-dependent relaxation produced by carbachol in aortic rings which is precontracted with NE was significantly lower in diabetic preparations than that in age-matched control animals. The EC50 of carbachol in diabetic and normal aortas to carbachol were 2.8 x 10(-6) M vs 1.2 x 10(-6) M respectively. These results suggest that deterioration of endothelium might exist in diabetic rats.