Abstract: Objective To explore the effects and related mechanisms of gestational diabetes mellitus on vascular endothelium of the offspring rats. Methods The day of vaginal plug existed firstly after the female mated with male was considered as day 0of pregnancy,when pregnant Sprague-Dawley rats received a single intraperitoneal injection of 35mg/kg streptozotocin to induce diabetes（n=6）. The control group were injected with saline（n=6）. Systolic blood pressures of the offspring were measured noninvasively and consistently. The reactivity of mesenteric arterial rings to acetylcholine（10-9-10-5 mol/L）and sodium nitroprusside（10-9-10-5 mol/L）were measured by vitro microvascular tension measurement system in 20-weeks old offspring. To estimate the effect of acetylcholine on arterial rings incubated for 30 minutes with nitric oxide synthase inhibitor（Nω-nitro-L-arginine-methyl-ester,l-NAME,10-5 mol/L）by measuring the level of endogenous endothelial nitric oxide synthase（eNOS）and nitric oxide. Results The offspring of the rats treated with streptozotocin had higher systolic blood pressure than control group at 12,16,20 and 24weeks of age（118±4）vs（105±3）,（124±2）vs（114±4）,（135±3）vs（118±2）,（140±4）vs（120±3）mm Hg,respectively,all P＜0.01. Compared to control group,the maximal relaxant effect of acetylcholine was significantly weakened in streptozotocin group（72.2±3.3）% vs（95.6±2.7）%,P＜0.05,while there was no significant difference of nitroprusside caused maximal relaxant effect between the two groups.The acetylcholine induced vasodilation effect could be significantly weakened by incubating withl-NAME. In the offspring of streptozotocin group,the level of eNOS in the mesenteric arteries did not change significantly,while the phosphoeNOS expression decreased,as well as the production of nitric oxide. Conclusion Gestational diabetes mellitus induced blood pressure elevation of the offspring may related to the limited production of nitric oxide,which could damage the vasorelaxation.