Flow-mediated vasodilation and distensibility of the brachial artery in renal allograft recipients

Background. Alterations of large artery function and structure are frequent ly observed in renal allograft recipients. However, endothelial function ha s not yet been assessed in this population. Methods. Flow-mediated vasodilation is a useful index of endothelial functi on. We measured the diameter and distensibility of the brachial artery at r est using high-resolution ultrasound and Doppler frequency analysis of vess el wall movements in the M mode. Thereafter, changes in brachial artery dia meter were measured during reactive hyperemia (after 4 min of forearm occlu sion) in 16 cyclosporine-treated renal allograft recipients and 16 normal c ontrols of similar age and sex ratio. Nitroglycerin-mediated vasodilation w as measured to assess endothelium-independent vasodilation. Brachial artery blood pressure was measured using an automatic sphygmomanometer, and brach ial artery flow was estimated using pulsed Doppler. Results. Distensibility was reduced in renal allograft recipients (5.31 +/- 0.74 vs. 9.10 +/- 0.94 x 10(-3)/kPa, P = 0.003, mean +/- SEM), while the b rachial artery diameter at rest was higher (4.13 +/- 0.14 vs. 3.25 +/- 0.14 mm, P < 0.001). Flow-mediated vasodilation was significantly reduced in re nal allograft recipients (0.13 +/- 0.08 vs. 0.60 +/- 0.08 mm or 3 +/- 2 vs. 19 +/- 3%, both P < 0.001). However, nitroglycerin-mediated vasodilation w as similar in renal allograft recipients and controls (0.76 +/- 0.10 vs. 0. 77 +/-. 0.09 mm, NS, or 19 +/- 3 vs. 22 +/- 2%, NS). There were no signific ant differences in brachial artery flow at rest and during reactive hyperem ia between both groups. The impairments of flow-mediated vasodilation and d istensibility in renal allograft recipients remained significant after corr ection for serum cholesterol, creatinine, parathyroid hormone concentration s, end-diastolic diameter, as well as blood pressure levels, and were also present in eight renal allograft recipients not treated with cyclosporine. Flow-mediated vasodilation was not related to distensibility in either grou p. Conclusions. The results show impaired endothelial function and reduced bra chial artery distensibility in renal allograft recipients. The impairments of flow-mediated vasodilation and distensibility are not attributable to a diminished brachial artery vasodilator capacity, because endothelium-indepe ndent vasodilation was preserved in renal allograft recipients.