Cardiac voltage-gated sodium channel expression and electrophysiological characterization of the sodium current in the zebrafish (Danio rerio) ventricle

Na+ channel alpha-subunit composition of the zebrafish heart and electrophysiological properties of Na+ current (I-Na) of zebrafish ventricular myocytes were examined. Eight Na+ channel alpha-subunits were expressed in both atrium and ventricle of the zebrafish heart. Na(v)1.5Lb, an orthologue to the human Na(v)1.5, was clearly the predominant isoform in both chambers representing 65.2 +/- 4.1% and 83.1 +/- 2.1% of all Na+ channel transcripts in atrium and ventricle, respectively. Na(v)1.4b, an orthologue to human Na(v)1.4, formed 34.1 +/- 4.1 and 16.2 +/- 2.0% of the Na+ channel transcripts in atrium and ventricle, respectively. The density of I-Na and the rate of action potential upstroke in zebrafish ventricular myocytes at 28 degrees C were similar to those of human ventricles at the comparable temperature. Na+ channel isoforms and the main electrophysiological characteristics of the I-Na are largely similar in zebrafish and human hearts indicating evolutionary conservation of Na+ channel composition and function. The zebrafish I-Na differs from the human cardiac I-Na in terms of higher tetrodotoxin sensitivity (IC50-value = 5.3 +/- 0.1 nM) and slower inactivation kinetics. The zebrafish I-Na was inhibited with tricaine (MS-222) with an IC50-value of 1.2 +/- 0.18 mM (336 mg l(-1)), suggesting some care in the use of MS-222 as an anesthetic. (C) 2018 Elsevier Ltd. All rights reserved.