Abstract
Background: Endothelial dysfunction occurs in patients with end-stage renal disease (ESRD) and is associated with
increased cardiovascular morbidity and mortality. Asymmetric dimethylarginine (ADMA) contributes to endothelial
dysfunction in ESRD. In the general population, angiotensin-converting enzyme (ACE) inhibitors and angiotensin
receptor blockers (ARBs) decrease ADMA levels, but no study has compared the effect of these drugs in patients
with ESRD on maintenance hemodialysis (MHD).
Methods: We evaluated the effect of 1-week treatment with ramipril (5 mg/d), valsartan (160 mg/d), and placebo
on ADMA levels in 15 patients on MHD in a double-blind, placebo-controlled, three x three cross-over study.
Results: We found that ADMA levels were increased at baseline and throughout the dialysis session during ramipril
treatment (p < 0.001 compared to both, placebo and valsartan). Ramipril did not increase ADMA levels in a study of
patients without ESRD, suggesting that factors related to ESRD or hemodialysis contribute to the ACE inhibitor-induced
increase in ADMA. We have previously shown that ACE inhibition increases bradykinin (BK) levels during hemodialysis.
We therefore evaluated the effect of bradykinin on ADMA production in A549 cells; a cell line that expresses BK receptors.
Incubation with BK increased intracellular ADMA concentration through BK B2-receptor stimulation.
Conclusion: These data indicate that short-term ACE inhibition increases ADMA in patients on MHD whereas
ARBs do not. In vitro studies further suggest that this may occur through BK-mediated increase in ADMA
production during ACE inhibition.
Trial registration: Clinicaltrials.gov NCT00732069 August 6 2008 and NCT00607672 February 4 2008
Keywords: Asymmetric dimethylarginine, Hemodialysis, Angiotensin converting enzyme inhibitors, Angiotensin
receptor blocker
 
AbstractBackground: Endothelial dysfunction occurs in patients with end-stage renal disease (ESRD) and is associated withincreased cardiovascular morbidity and mortality. Asymmetric dimethylarginine (ADMA) contributes to endothelialdysfunction in ESRD. In the general population, angiotensin-converting enzyme (ACE) inhibitors and angiotensinreceptor blockers (ARBs) decrease ADMA levels, but no study has compared the effect of these drugs in patientswith ESRD on maintenance hemodialysis (MHD).Methods: We evaluated the effect of 1-week treatment with ramipril (5 mg/d), valsartan (160 mg/d), and placeboon ADMA levels in 15 patients on MHD in a double-blind, placebo-controlled, three x three cross-over study.Results: We found that ADMA levels were increased at baseline and throughout the dialysis session during ramipriltreatment (p < 0.001 compared to both, placebo and valsartan). Ramipril did not increase ADMA levels in a study ofpatients without ESRD, suggesting that factors related to ESRD or hemodialysis contribute to the ACE inhibitor-inducedincrease in ADMA. We have previously shown that ACE inhibition increases bradykinin (BK) levels during hemodialysis.We therefore evaluated the effect of bradykinin on ADMA production in A549 cells; a cell line that expresses BK receptors.Incubation with BK increased intracellular ADMA concentration through BK B2-receptor stimulation.Conclusion: These data indicate that short-term ACE inhibition increases ADMA in patients on MHD whereasARBs do not. In vitro studies further suggest that this may occur through BK-mediated increase in ADMAproduction during ACE inhibition.Trial registration: Clinicaltrials.gov NCT00732069 August 6 2008 and NCT00607672 February 4 2008Keywords: Asymmetric dimethylarginine, Hemodialysis, Angiotensin converting enzyme inhibitors, Angiotensinreceptor blocker
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