In this study, we investigated the effect of NO donor, diethylamine/nitric oxide (DEA/NO), on the electrophysiological behavior of human skeletal muscle chloride channel (CLCN1). The wild-type and variants of CLCN 1, including one polymorphism (P727L) and four mutants (T631I. D644G, G482R, and S471F), were expressed in Xenopus oocytes and the ionic current was measured by two-electrode voltage-clamp method. Our results revealed that there is no significant difference in the current-voltage relationships and half-voltage values of open probability between wild-type and variants of CLCN1 except for G482R. Application of the DEA-NO (0.1 mM) significantly increases the channel conductance of wild-type, T631I, D644G, and S471F, but not P727L. This indicates that P727L polymorphism causes loss of sensitivity of CLCN1 to the DEA/NO treatment, which could be due to a conformational change caused by proline substitution. The data suggest that the polymorphic changes may affect the function of CLCN1 in response to the treatment of chemical compounds. (c) 2007 Elsevier Inc. All rights reserved.