Vitamin C improves endothelial dysfunction in renal allograft recipients

Background. Endothelial function is impaired in renal allograft recipients but the effects of antioxidant vitamin therapy on endothelial function in s uch patients is unknown. Methods, Thirteen renal allograft recipients were randomized to vitamin C o r placebo in a double blind cross-over study design. Flow-mediated endothel ium-dependent dilation and glyceryltrinitrate-induced endothelium-independe nt dilation of the brachial artery were assessed before and 2 h after oral administration of 2 g vitamin C or placebo. Results, Plasma vitamin C levels increased 33.5 +/- 17.0 mu mol/l to 98.8+/ -60.2 mu mol/l after treatment (P=0.0001). Endo thelium-dependent dilation improved (from 1.6 +/- 2.6 to 4.5 +/- 2.5%) after vitamin C administration but was unchanged after placebo (1.9 +/- 1.5 to 1.8 +/- 2.5%; P = 0.003 for vitamin C vs placebo). There was no significant change in endothelium-inde pendent dilation in response to vitamin C. Vitamin C was also associated wi th a significant increase in the lag time in dilute serum oxidation (P = 0. 001). Conclusions. Vitamin C acutely improves mediated, endothelium-dependent dil ation increases the resistance of lipoproteins in ( serum to oxidation in r enal transplant recipients.