Phenanthrene affects cardiovascular function in the developing African clawed frog (Xenopus laevis)

Abstract

The incomplete combustion of fossil fuels results in deposition of the tricyclic aromatic hydrocarbon phenanthrene into air, soil, and water. This common and persistent contaminant is also present in tobacco smoke, coal tar sealant, and weathered crude oil. Surprisingly, little is known about its toxicity. To gain a better understanding of potential risks to humans, we characterized the effects of phenanthrene exposure using embryos of X. laevis, an important model for vertebrate development. Heart rates and evidence of arrhythmia were recorded during various stages of heart development using an inverted dissecting microscope, Leica™ camera, and the video recording and editing software Camtasia.™ In stage 42 embryos, phenanthrene exposure (5 ppm, 28.5 μM) led to bradycardia with a decrease to 79% of control values at 6 hrs followed by a further reduction to 69% by 10 hrs. After 5 hrs of depuration, heart rates returned to control levels. Arrhythmia was also evident in phenanthrene‐exposed embryos. A 42% increase in interbeat variability was observed following a 10‐hr exposure to 5 ppm. These phenanthrene‐induced effects may be stage‐specific as cardiac function in stage 47 animals, with a mature morphology, and in stage 37 animals was less affected. These findings underscore the need for further characterization of the cardiotoxic effects of this common pollutant.(Supported by NH‐INBRE grant 1P20RR030360‐01)