维生素C和硝酸甘油合用对硝酸甘油耐受性的影响

目的：观察维生素C（VitC)和硝酸甘油（NTG）合用对NTG耐受性的影响，并探讨其机制。方法：测定累积浓度的NTG对兔离体动脉环的舒张程度和静脉注射NTG1mg/kg后兔平均动脉压下降的幅度，以此来判断各组动物对NTG耐受的程度，测定免血管组织中丙二醛（MDA）、一氧化氮（NO）和环磷酸鸟苷（cGMP)的含量。结果：持续应用NTG贴片3日后，NTG组和NTG＋Vit组免均对NTG所产生了耐受，但后耐受的程度显低于前（P＜0。01）；NTG＋VitC组免血管组织中NO和cGMP的含量显高于NTG组（P＜0．01），而MDA的含量显低于NTG组（P＜0．01）。结论：VitC和NTG合用具有显改善NTG耐受性的作用，其机制可能与Vit能够减少NTG源性NO的失活有关。

Effect of concomitant administration of Vit C on the development of nitroglycerin tolerance

Objective:To evaluate the effects of vitamin C(Vit C),an antioxidant,on the development of nitroglycerin(NTG) tolerance during continuous NTG patches therapy.Methods:After 3 days of NTG patches with and without concomitant administration of Vit C,relaxations to cumulative concentrations of NTG in rabbit aortic ring segments and hypotentive responses to NTG(1mg/kg) intravenous injection in chronically catheterized rabbits were examined to judge the degree of NTG tolerance.Vascular malondialdeyde(MDA),nitric oxide(NO) and cyclic guanosine monophosphate (cGMP) levels were measured at the end of the treatment.Results:Both in NTG Group and NTG+Vit C group,relaxations of aorta rings to cumulative concentrations of NTG were attenuated vs controls( P <0 01):Responses to NTG were attenuated to a greater extent in NTG group vessels than NTG+Vit C group vessels( P <0 01).The hypotensive response to NTG intravenous injection in NTG+Vit C group was higher than that in NTG group significantly( P <0 001),but still lower than that before continuous NTG patches application( P <0 01).Vascular MDA level in NTG group was significantly higher than that in NTG+Vit C group( P <0 01),while vascular NO and cGMP levels were significantly lower than those in NTG+Vit C group( P <0 01).Conclusion:NTG tolerance could be modified significantly by concomitant therapy with Vit C.The possible mechanism of this phenomenon is that Vit C can prevent the inactivation of NTG derived nitric oxide.