Abstract: Objective To study the inhibitory effects of asymmetric dimethyl arginine(ADMA) on endothelium-dependent vasodilation(EDVD) of human radial arteries. Methods Vascular rings were obtained from patients under maintenance hemodialysis(MHD) during internal arteriovenous fistula operation. According to the conditions of the endothelium, the arteries were divided into two groups: the endothelium intact group, and the endothelium deprived group, in which the endothelium was extracted mechanically. The arteries were then mounted on wire myographs. Contraction of the arteries were invoked with 10^-5 mol/L phenylephrine(PE), while EDVD was caused by a dose of 10^-5 mol/L acetylcholine(ACh) for the endothelium intact group or 10^-7 mol/L sodium nitroprusside(SNP) for the endothelium deprived group. Different concentrations of ADMA(10^-7~10^-3 mol/L) were used to test its inhibitory effects on EDVE. Cumulative concentration-response curves were then constructed for AMDA. Results For the endothelium intact group, the dilatation reached 67.10%±18.63%, when the arteries were subjected to 10^-5 mol/L ACh after PE(10^-5 mol/L)treatment. The inhibitory effects of ADMA on ACh-invoked EDVD were concentration-dependent. The relative contraction rates according to the concentrations of ACh were 7.32%±8.60%(ACh 10^-7 mol/L), 20.03%±13.49%(ACh 10^-6 mol/L), 29.93%±11.78%(ACh 10^-5 mol/L), 43.30%±11.29%(ACh 10^-4 mol/L), 80.21%±18.16%(ACh 10^-3 mol/L). For the endothelium deprived group, ADMA had a weak inhibitory effect on the endothelium independent vasodilatation(EIVD) caused by SNP. There were no concentration-dependent changes according to the concentration of ADMA. Relative constriction rates were 2.76%±1.98%(ADMA 10^-7 mol/L), 2.27%±1.82%(ADMA 10^-6 mol/L), 3.38%±2.99%(ADMA 10^-5 mol/L), 3.59%±3.66%(ADMA 10^-4 mol/L), 4.16%±3.67%(ADMA 10^-3 mol/L). Conclusion The results suggest that ADMA can inhibit EDVD caused by ACh. This effect is ADMA concentration-dependent, and endothelium-dependent.

Key words: asymmetric dimethyl arginine, endothelium-dependent vasodilatation, radial artery