Assessment of endothelial function by acetylcholine iontophoresis: Impact of inter-electrode distance and electrical cutaneous resistance Cyril Puissant a , Pierre Abraham a,b , Sylvain Durand c , Anne Humeau-Heurtier d , Sébastien Faure e , Georges Leftheriotis a,b , Guillaume Mahé f,g, ⁎ a Laboratory of Vascular Investigations, University Hospital of Angers, France b L'UNAM University, University of Angers, Biologie Neurovasculaire et Mitochondriale Intégrée (BNMI), Unité mixte UMR CNRS 6214/INSERM U 1083, Medicine Faculty, Angers, France c L'UNAM University, University du Maine, bEA 4334N, Motricity, Interactions, and Performance, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France d L'UNAM University, University of Angers, LARIS — Laboratoire Angevin de Recherche en Ingénierie des Systèmes, 62 avenue Notre Dame du Lac, 49000 Angers, France e L'UNAM University, University of Angers, INSERM UMR 1063, Stress oxydant et pathologies métaboliques (SOPAM), Angers, France f CHU Rennes, Imagerie Coeur-Vaisseaux, F-35033 Rennes, France g INSERM Clinical Investigation Center CIC 1414, F-35043 Rennes, France abstract article info Article history: Accepted 4 April 2014 Available online 13 April 2014 Objectives: Endothelial function can be assessed by acetylcholine (ACh) iontophoresis with single current appli- cation. The effect of inter-electrode distance as well as electrical cutaneous resistance (ECR) on ACh dependent vasodilation has never been studied using single current application. The aims of this study are (i) to compare ACh-peak and ECR measured at different inter-electrode distances, (ii) to assess the relationship between ACh-peak and ECR, (iii) and to study the reproducibility of the ECR values. Methods: Fourteen healthy subjects were included. Using laser speckle contrast imaging, ACh-iontophoreses (0.1 mA, 30 s) were performed on the forearm at a 7-day interval with an inter-electrode distance set at 5 cm. Two other inter-electrode distances were also evaluated: 10 cm and 15 cm. ECR was measured during each ACh-iontophoresis as well as the ACh-peak. Results: No statistical difference was found between the ACh-peak values obtained at 5 cm, 10 cm and 15 cm. ECRs were also not statistically different. An inverse relationship (r = -0.60) was found between the ACh-peak and ECR (p b 0.05). The coefficient of variation of the inter-day reproducibility of the ECR values was 9.1% [6.5%–15.1%] with an intra-class-correlation coefficient of 0.93 [0.81–0.98]. Conclusion: Inter-electrode distance ranging from 5 cm to 15 cm changes neither the ACh-peak value nor the ECR value. ECR impacts ACh-peak values. © 2014 Elsevier Inc. All rights reserved. Introduction Endothelial dysfunction appears as an essential element in the early onset of cardiovascular disease (Deanfield et al., 2007; Turner et al., 2008). It is therefore of interest to develop techniques to assess the en- dothelial function in order to screen population for estimating the sub- jects' cardiovascular risk. In recent years, numerous methods have been developed and used to assess endothelial function at different levels: heart level and peripheral level (Flammer et al., 2012; Lekakis et al., 2011). The recently developed laser speckle contrast imaging (LSCI) tech- nique has been shown to be of interest for peripheral endothelial tests (Mahe et al., 2013; Puissant et al., 2013, 2014; Humeau-Heurtier et al., 2013 with the following reference:Relevance of laser Doppler and laser speckle techniques for assessing vascular function: state of the art and fu- ture trends. Humeau-Heurtier A, Guerreschi E, Abraham P, Mahé G.IEEE Trans Biomed Eng. 2013 Mar;60(3):659-66). LSCI is based on the speckle phenomenon and explores the skin microcirculation up to a depth of nearly 300 μm(Mahe et al., 2012c; O'Doherty et al., 2009). LSCI measure- ments have a good reproducibility compared with other flowmetry tech- niques (Roustit et al., 2010; Tew et al., 2011;Puissant et al., 2013). It can be coupled with different pharmacological tests: the microdialysis and the iontophoresis (Mahe et al., 2012c). Microdialysis is an invasive method whereas the iontophoresis is a non-invasive one (Cracowski et al., 2011). Iontophoresis allows transdermal drug delivery using current ap- plication during a specific duration (Tesselaar and Sjoberg, 2011). More- over, iontophoresis is safe and painless since low intensity currents are used. Depending on the charged drug used, different physiological path- ways can be assessed (Khan et al., 2004; Mahe et al., 2012c; Tesselaar and Sjoberg, 2011). When acetylcholine (ACh) is used as an iontophoresed drug, the endothelial function can be studied (Cordovil Microvascular Research 93 (2014) 114–118 ⁎ Corresponding author at: Imagerie Coeur-Vaisseaux, University Hospital, 2, Rue Henri Le Guilloux, 35033 Rennes Cedex 9, France. Fax: +33 2 99 28 43 64. E-mail addresses: guillaume.mahe@chu-rennes.fr, maheguillaume@yahoo.fr (G. Mahé). http://dx.doi.org/10.1016/j.mvr.2014.04.001 0026-2862/© 2014 Elsevier Inc. All rights reserved. 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