Exploration of human, rat, and rabbit embryonic cardiomyocytes suggests K-channel block as a common teratogenic mechanism

Abstract

Aims Several drugs blocking the rapidly activating potassium (K r) channel cause malformations (including cardiac defects) and embryonic death in animal teratology studies. In humans, these drugs have an established risk for acquired long-QT syndrome and arrhythmia. Recently, associations between cardiac defects and spontaneous abortions have been reported for drugs widely used in pregnancy (e.g. antidepressants), with long-QT syndrome risk. To investigate whether a common embryonic adverse-effect mechanism exists in the human, rat, and rabbit embryos, we made a comparative study of embryonic cardiomyocytes from all three species.Methods and resultsPatch-clamp and quantitative-mRNA measurements of Kr and slowly activating K (Ks) channels were performed on human, rat, and rabbit primary cardiomyocytes and cardiac samples from different embryo-foetal stages. The Kr channel was present when the heart started to beat in all species, but was, in contrast to human and rabbit, lost in rats in late organogenesis. The specific Kr-channel blocker E-4031 prolonged the action potential in a species- and development-dependent fashion, consistent with the observed Kr-channel expression pattern and reported sensitive periods of developmental toxicity. E-4031 also increased the QT interval and induced 2:1 atrio-ventricular block in multi-electrode array electrographic recordings of rat embryos. The Ks channel was expressed in human and rat throughout the embryo-foetal period but not in rabbit.ConclusionThis first comparison of mRNA expression, potassium currents, and action-potential characteristics, with and without a specific K r-channel blocker in human, rat, and rabbit embryos provides evidence of Kr-channel inhibition as a common mechanism for embryonic malformations and death. © 2012 Published on behalf of the European Society of Cardiology. All rights reserved.