The role of endothelial cells on the alterations in vascular reactivity induced by insulin-dependent diabetes mellitus: effects of insulin treatment.

1. In this study, the maximal contractile responses to noradrenaline (NA) were significantly increased but pD2 values (sensitivity) were not significantly altered in aortas with endothelium from insulin-dependent (ID)-diabetic rats when compared to their controls. 2. Removal of the endothelium resulted in a significant increase in the maximum response of control and ID-diabetic aortas and also loss of the difference in maximum contractile response to NA between ID-diabetic aortas and their corresponding controls. 3. Endothelium-dependent relaxation stimulated by acetylcholine (ACh), methacholine, histamine, ATP and insulin, in aortic rings precontracted with NA were significantly attenuated but unchanged by A23187 in ID-diabetic vessels relative to controls. 4. Relaxations produced by sodium nitroprusside (SNP) in ID-diabetic aortas were similar to those in control vessels. 5. The sensitivity of ID-diabetic aortas to relaxant substances were not changed when compared with controls. 6. These results demonstrate that ID-diabetes-induced specific changes in vascular reactivity and endothelial cells have an important role on the maintenance of vascular tonus. This feature may be responsible for the major complications of diabetes such as macroangiopathy, vasospasm and high blood pressure in late stage of the disease.