Vitamin C augments the renal response to L-arginine in smokers

Background. In the coronary and the forearm circulations, endothelium-dependent vasomotion is impaired in smokers, but can be augmented by L-arginine or vitamin C. We examined whether smoking similarly affects the renal circulation. Methods. In 20 smokers (age 26 4 years) and in 20 non-smokers (age 28 3 years) changes of renal plasma flow (RPF), glomerular filtration rate (GFR), blood pressure and heart rate in response to the subsequent intravenous infusions of NG-monomethyl-L-arginine (L-NMMA), L-arginine and L-arginine plus vitamin C were studied by use of a constant infusion input clearance technique. Results. Systemic haemodynamic parameters did not differ between smokers and non-smokers during each experimental phase. At baseline, RPF and GFR were similar between the groups. The infusion of L-NMMA led to a similar decrease of RPF, while GFR did not change in either group. During the infusion of L-arginine RPF increased similarly. Finally, the co-infusion Of L-arginine plus vitamin C led to a significantly greater increase of RPF (+277 +/- 395 vs +79 +/- 76 ml/min, P=0.03) and GFR (+ 12.1 +/- 10.6 vs. + 3.4 +/- 11.2 ml/min, P = 0.02) in smokers as compared to non-smokers. Conclusions. L-NMMA-induced vasoconstriction of the renal vasculature was similar in smokers compared to non-smokers. L-arginine alone induced a similar increase of RPF. The co-infusion of vitamin C and L-arginine led to a greater increase of RPF and GFR in smokers. This might suggest that oxidative stress is increased in the renal vasculature of smokers.